With more than 15 years experience in the hydroponics industry, we have advised many growers on how to run successful grow rooms, all year round. During this time, we have found that growers tend to encounter more problems in summer. This is mainly due to higher temperatures. However, by following good grow room practices you can still grow strong and healthy plants in summer. Here we explain how:
Step By Step Summer Growing
When you walk/look into your grow room, do a quick visual check and make sure that the lights are running, fans are on, and there are no obvious problems - such as puddles on the floor or Mylar hanging off the wall. You should also check that your plants look healthy. For instance, are your plants producing new shoots? Are they a nice colour, i.e. are they lush and vibrant? Does there appear to be any leaf curl?
Both temperature and relative humidity have a great influence on your plants’ overall development. We recommend that you purchase a maximum/minimum thermo-hygrometer which will allow you to check the maximum and minimum temperature and relative humidity between your grow room visits.
For healthy plant growth, the ideal grow room temperature is between 22-28°C. If your maximum temperature reaches 30°C or more, you will need to think about ways to cool your room down. For example, you could upgrade your extractor fan. It may also be worth investing in air-cooled reflectors, an air conditioning unit and/or a humidifier. Turning off one of your lights is also an option.
Your plants will perform best when relative humidity is between 50-75%. If your minimum humidity is below 45%, you should think about ways of increasing this, for example by purchasing a humidifier or mist maker.
Running a grow room with a low relative humidity and high temperature is the cause of most problems growers encounter in summer. Both can cause your plants to become stressed through excess water loss. This, in turn, can initiate over-fertilization because your plants will use more water and leave behind nutrient. Consequently, this can result in leaf curl and burnt tips.
Ideally, you should aim for a nutrient temperature of approximately 21°C. Purchase a good thermometer to keep track of the water temperature. If your nutrient solution is too hot (above 24°C), try covering up your tank with reflective sheeting, which will help to reflect any heat/light that may heat your solution.
You will also need to check that your nutrient reservoir is set at the right pH and nutrient strength (CF) for the size/age of your plants. As a general guide, the ideal CF range is between 10-16 during the vegetative cycle and 16-24 in flowering.
As mentioned earlier, over-fertilization can be more prominent during summer, particularly in recirculating systems. If you find the CF is too high in your reservoir, dilute your nutrient with water. A flush of your system or growing media may be necessary.
However, if you find you have to add a lot of water every day, it’s likely that your relative humidity is too low. If so, we advise running your nutrient at a lower strength and that you consider investing in a humidifier.
If you’re using an NFT system, make sure that your flow rate isn’t too high or low, and if you use drippers turn the pump on quickly to make sure you have no blockages.
We advise that you check your plants thoroughly at least once every three days, ideally every day if you can. When looking at the base of your plants, make sure that you’re growing media isn’t too wet or dry, and if you’re growing in growing in an NFT system, such as the NFT Gro-Tank Kit, that the roots are healthy, i.e. plenty of white growth.
You will also need to check your plants for insects, which can be rife in summer. Look at the leaves of your plants from the base of the plant up. Insects, such as spider mite and thrips prefer to live and breed on the underside of leaves, so be sure to check here too. You may wish to purchase a magnifier to help you check and correctly identify insects.
If you find any insect activity, act quickly by either spraying the affected leaves/plants with an insect killer and/or remove extremely damaged leaves. Note: Insects can breed extremely fast when temperatures are high.
Below is a list of some final checks you should make before you leave your grow room:
What does organic mean? Other than the traditional scientific definition of ‘containing carbon’, organic growing is a term now used to describe a more natural, holistic approach to growing plants. This encompasses avoiding the use of chemical pesticides, fungicides and artificial fertiliser/ liquid nutrients.
Typically, in an organic garden, the grower will be using an organic growing media that is free from chemicals and is biodegradable along with dry or liquid nutrients and additives that contain plant or animal extracts, not refined mineral salts (chemicals).
When you grow a plant using organic growing media and nutrients, there are some differences in the way the plant has access to nutrition in comparison to hydroponics.
In hydroponics, the plants are given nutrients that are already in an ‘available form’. This means the nutrients are taken up into the roots straight away.
When you water your soil with an organic nutrient, most of the elements that end up in and around the root zone cannot be taken up straight away by the plant. The elements need to be converted into a form that the plant can use - this is done by small microbes in the soil (bacteria, enzymes, fungi and protozoa) and the process is known as mineralisation. This means that the health of your soil becomes very important as it is a living system that nourishes the plant.
Deciding to grow organically is often a conscious choice to try and grow plants in the most natural way possible. But in reality, there are not many extra benefits when compared to hydroponic growing. Organic growing is slower than hydro - especially in vegetative growth - but it is a lot easier to maintain than a hydroponic system.
Controlling the nutrition in the root zone is more difficult because of the lag time between using
the nutrients and them being available to the plant. This uncertainty with feeding is often counteracted by using nutrients every other watering or using water only once a week. If you ask an avid organic gardener, they will tell you that you develop a ‘feel’ for what the plants need. It is this predictive interaction with the plants that a lot of organic growers learn to love and take pleasure in.
There are many brands of nutrients and soils that will claim to be organic. To be certain that you are using quality products, make sure that they have certification from a recognised organisation. There are many organisations world wide that will approve a product as organic, but you must be aware that these organisations have different standards. Look for one of the following widely accepted organisations to be sure of its quality:
At Aquaculture, we firmly believe that BIOBIZZ are the market leaders in supplying top quality products to produce organic crops. Certified by OMRI, their products are of premium quality and produce excellent results. We have many happy organic growers that have been using BIOBIZZ nutrients since we started selling them in early 2000.
How Do I Grow Organically?
For more detailed instructions on how to grow using soil and liquid nutrients please refer to our ‘Growing in Soil’ article.
What equipment do I need?
Pots and saucers, certified compost/soil, certified liquid nutrients, and lighting and ventilation as with any indoor garden.
5 Top Tips:
Light is one of the most important factors to consider when growing plants. It is very simple - no light means no growth. In fact, as a general rule, the more light your plants have access to, the quicker they will grow and the more they will yield. The benefit of an indoor grow light is that it allows you to grow literally any plant, anywhere, anytime! However, to get the best out of your indoor grow light – and growing – it is helpful to understand the basic principles of light.
Spectrum Anyone who has seen a rainbow will know that sunlight is made up of different colours. These colours of light can also be differentiated by their wavelength which is measured in nanometers (nm).
The human eye is most sensitive to light around the middle of the visible spectrum - between 500 and 600nm. Plants find wavelengths between 400 and 700nm useful for turning light into energy (photosynthesis), and this area is referred to as Photosythetically Active Radiation – commonly abbreviated to PAR. While the human eye finds light at 555nm the most visible (thus more useful), plants find two distinct areas of the spectrum most useful – the blue area between 400-460nm and the red area between 580-700nm.
(Diagram reprinted with permission from Gavita Holland > www.gavita-holland.com)
Measuring Light Lumens is a measurement of light intensity, and is often used to define the output from artificial lights. This is fine for lights to help us see in the dark, but becomes rather useless when measuring horticultural grow lights because lumens are measured according to what the eye is sensitive to. Using lumens is therefore not a correct representation of the properties of a lamp that are useful to plants.
Lux is often used by light-measuring devices and is simply a measurement of how many lumens fall on each square meter of surface. So an illumination of 50,000 lux is 50,000 lumens falling on each square meter. Lux measurements are useful for measuring intensity from grow lamps and can be used to determine an accurate height to position the light above the plants, or to check for lamp degradation. However, lux is still not a good measurement for determining the quality of light and how good it is for growing plants.
Professional growers and light manufacturers have switched from measuring light in lumens and lux, to photon count in the PAR area. Without going into too much detail, a photon is a particle of light. A blue photon has a short wavelength and does not have as much energy as a red photon - which has a long wavelength. The plant, however, is only interested in the number of photons (it does not use the energy in the photon for photosynthesis). A plant requires 8-10 photons to bind one molecule of CO2. So a blue 600W light produces less photons than a red 600W light and is less efficient for photosynthesis. However, you do need more than just red colours in your spectrum for a plant to grow healthily.
A device to measure photons is called a quantum meter. The total amount of photons - known as the photosynthetic photon flux (PPF) - from a lamp can be measured with a quantum meter to give you accurate data on the amount of photons per second coming from your lamp. Photons are counted in micromoles (µmol) – and in case you are interested, one µmol is 602214150000000000 photons! The unit used for PPF is micromole/second (µmol/s), and a good 600W HPS lamp will emit 1100 µmol/s.
To summarise, if you have two lights and one has a higher lumen output, it is not an indication that it is better for growing plants. The most useful light output data is plant useable light measured in micromoles.
Day Length The amount of light your plant receives in a 24 hour period is called the ‘photoperiod’ or day length. Some plants use the photoperiod as a signal to know when to produce leaves, flowers or fruit. Using this signalling tool, indoor growers can alter the photoperiod using timers to control their lights and their plants. Long day lengths of 16-24 hours are most commonly used for vegetative growth, and short light cycles of 12 hours are used for flowering or fruiting. Most grow lights are too powerful for plug in timers, the solution to this this will be covered later.
Light and Environment
All lights produce some heat as well as light. When growing indoors this heat generated by the grow lights need to be removed using an extractor fan to keep the plants growing environment comfortable. If you position your light too close to your plants, the heat from the lamp may burn them. So, it is very important to correctly hang your growing lights.
Types of Grow Lights There are two categories of lights commonly used for growing plants. These are fluorescent and high intensity discharge (HID).
Fluorescent Grow Lights Fluorescent grow lights are more suitable for propagation and vegetative growth. They have good colour rendering properties (a high proportion of the light emitted is used by the plant) and produce less heat than HID grow lights (see below). This allows them to be placed closer to your plants to make the most of their output.
There are two types of fluorescent lights used for growing - Compact Fluorescent Lamps (CFL) and T5 lamps (aka tubes). CFL’s are large ‘energy saving’ lamps and have the electronics to ignite the lamp at their base. These can be screwed into a reflector or simply hung vertically above the crop. T-5’s are the most efficient fluorescent tube light, and need separate electronics to ignite the lamps. These electronics are housed within T5 reflectors. Due to the size of the T5 tubes, they produce a very uniform level of light over a larger area in comparison to CFL’s.
Compact Fluorescents are available in 150W and 250W, as well as a propagation lighting system utilising 2 x 55W PL lamps. T5’s are available as 2ft 24W lamps and 4ft 54W lamps. These are available individually without a reflector or as an integrated lighting system with two, four or eight lamps.
Fluorescent lights are great for seedlings and cuttings, as plants at this stage do not need intense light. Both CFL and T5 are low intensity, so they need to be placed close to plants to be effective at promoting growth. If using fluorescent lights above propagators, do not place them too close as this will cause the internal propagator temperature to get too high.
The light emitted from a fluorescent lamp can vary depending on the lamp colour. Fluorescent lamps come in different colour variations differentiated by the Kelvin colour temperature scale. The Kelvin scale has become industry standard for differentiating commercial and domestic lighting, but is rarely referred to in horticultural lighting other than for fluorescent lamps.
Fluorescent lamps with a high Kelvin are mainly used for propagation or vegetative growth; these usually come in around 6400K. Lamps with a low Kelvin are used for flowering and usually emit light around 2700K. A mixture of both (1 x 27K for every 3 x 64K) is a good approach for vegetative growth , and the reverse (3 x 27K for every 1 x 64K) fruiting or flowering.
Due to their lower light output, fluorescent grow lights should not be used instead of HID lights during the flowering stage. However, they are effective as supplementary lighting when hung in between your plants with CFL lamp hangers, or as side lighting with T5’s.
All of our fluorescent lights can be plugged into a timer to control the photoperiod. A relay or contactor is not necessary. HID Grow Lights HID (High Intensity Discharge) lighting is the most efficient way to convert electricity into light and is the most popular type of horticultural grow light. HID grow lights are available in a large choice of wattages; the most common are 250W, 400W, 600W and 10000W – with the 600W being the most popular option. A HID grow light is made up of three parts:
The Ballast which contains the necessary electronics to ignite and run the lamp. The Reflector that holds the lamp in position and reflects light down to the plants. The Lamp which can be either a High Pressure Sodium (HPS) or Metal Halide (MH).
Ballasts A ballast or ‘power pack’ is at the heart of a HID lighting system. There are 2 types of ballast available - standard electromagnetic ballast and the more recent electronic or ‘digital’ ballast. Both deliver a surge of electricity at a high voltage to ignite the HID lamp. After ignition, the ballast then regulates the electricity being delivered to the lamp for safe operation. Electronic ballasts are around 3-4% more efficient than electromagnetic ballasts, run quieter and can have dimming functions to control the lamp power.
Reflectors HID reflectors come in all shapes and sizes, but are all designed to do one job – reflect as much light as possible down onto your plants. The most efficient reflectors are about 95% efficient – meaning of the original 100% light from the lamp, 95% is emitted by direct light from the lamp or reflected light from the reflector. Basically, even the best reflector will have around a 5% loss. A reflector should also help to create a uniform spread of light while avoiding ‘hot spots’ of intense light. Some reflectors are sealed using a glass plate or tube and are air-cooled using an extractor fan to further reduce the heat emitted from the lamp and keep grow room temperatures down.
Lamps Metal Halide - MH
Metal Halide (MH) lights produce a lot of light in the blue spectrum. This colour of light encourages plant growth, particularly green, leafy growth and keeps your plants short and compact. MH lamps produce a broad spectrum of light (more so than HPS) and a small amount of UV which can help improve the quality of your produce. However, MH lamps are not as efficient as HPS, producing around 30-40% less micromoles.
High Pressure Sodium - HPS
High Pressure Sodium (HPS) lamps emit mainly orange-red light. This band of light is best for fruiting and flowering plants but can also be used for vegetative plants with good results. HPS lamps are the most efficient grow light currently available and produce the best yields. Standard HPS lamps are slightly deficient in the blue spectrum; to supplement this you can use fluorescent lights or use a ratio of three HPS lamps to one MH lamp in the flowering period. Some HPS lamps are termed ‘Dual Spectrum’, which means that have an enhanced output in the blue spectrum. Dual spectrum lamps are touted as being an all-in-one veg and flower lamp, but their spectrum is still much more suited to flowering plants. Best results will be achieved using a MH lamp for vegetative growth and HPS lamp for flowering.
If you want to supplement your HPS with extra CFL’s, use the 6400K ‘Cool White’ lamps as these will provide the blue light your HPS is missing.
Switching from a HPS to a MH lamp in the last 1-2 weeks of the plants life cycle can greatly improve the quality of your produce by enhancing essential oil production.
Relays and Contactors When a ballast starts up, it draws a large amount of electricity for a split second so that it ignites the lamp. This spike of high voltage is enough to burn out a standard plug-in timer, so to successfully turn a HID light on-and-off automatically, you need to use a relay or a contactor. These devices use the timer as a signal, and draw the power through a 13-amp plug, rather than through the timer. One 13-amp relay can switch 1 x 1000W, 3 x 600W, or 4 x 400W HID lighting systems. Contactors are more heavy duty than relays and are used for larger indoor gardens with 4 or more 600W lights.
Other Types of Grow Lights New technologies currently trying to improve horticultural lighting are light emitting diodes (LED’s) and light emitting plasma (LEP).
Unfortunately, there has been a glut of cheap LED’s that have been launched in the hydroponics market over the years that have all over-promised and under-delivered. Many companies make claims that their LED’s are more efficient than HPS, but currently there are still no LED units that can produce yields that are close to comparable.
However, LED’s are a very promising area for supplementing light to change or ‘steer’ the plants growth. The benefit of LED’s is they can be tuned to a specific wavelength to trigger a certain response or enhance a particular growth stage.
The common LED grow lights on the market that have a mixture of blue and red LED’s say they are tuned to match the two PAR peaks and drive targeted photosynthesis, but they are missing all of the other wavelengths (colours) that plants also need. Interestingly, the most promising LEDs to come to market during 2012 are the ‘full spectrum’ LED’s that are designed to produce light across the whole PAR spectrum. However, the diode wattage and unit cost still means LED’s are not able to replace HPS lamps.
Light emitting plasma has come to market for the purpose of ‘solar simulation’. They produce a very broad spectrum of light, including UV’s, which is close to natural sunlight.
LEP units can be used on their own for vegetative growth but are lacking in the red spectrum to produce a good yield of fruits or flowers. They are very good for supplementary light, particularly for adding in UV light to improve quality which is missing from most HPS lamp. The market leaders in LEP technology is Gavita Holland and we are sure there will be some great further developments in LEP lighting systems over the coming years.
HID Lighting - Helpful Tips What lighting should I use in my grow room?
Your choice of grow light should be decided by the size of your growing area. Each type of HID grow light is suitable for a specified area. For guidelines on the type and number of lights you can put in your growing are see below.
Lamp Area Coverage:
250 Watt = 0.25m2 - 0.5m2 400 Watt = 0.5m2 - 1m2 600 Watt = 1m2 - 1.5m2 1000 Watt = 1.5m2 - 2m2 Hanging height - due to the heat that is emitted from HID lights, you should hang your lighting system according to size. The following is the recommended distance between the lamp and the plant canopy.
250W = 30 - 40cm 400W = 40 - 60cm 600W = 50 - 70cm 1000W = 75 - 100cm Top Tips:
MH lamps emit more heat than HPS, so mounting heights will need to be adjusted depending on your lamp. Use the back of your hand as a guide; if it’s too hot for your hand it’s too hot for your plants.
How Much Will it Cost?
To get the operating cost per hour for light, take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Then multiply that number by the amount your electric company charges per kilowatt hour (you will find this at the top of your electricity bill). HID lights will use a little more than the stated wattage; a typical 600W system will use 640-660W. To find out the precise usage you can purchase a plug in power meter for less than £10, these will give you a digital reading of actual power consumption.
Example: A grower with 1 x 600W HPS lighting systems finds his power consumption is 655W per light.
(power consumption wattage / 1000) x electricity cost per kilowatt hour = Operating cost per hour 655 / 1000 = 0.655 Electricity cost = 12.5p per kWh 0.655 x 12.5 = 8.2p This grower is paying 8.2p for every hour his 600W light is on, that equates to £1.48 per day for vegetative growth (18 hours) and £0.98p per day for flowering growth (12 hours)
How do you provide a more uniform level of lighting?
If you find that your reflector is not throwing enough light out to the edges of your room, or is creating hot spots, you should look at investing in a better reflector to improve uniformity. If you are using a high wattage HID light such as a 1000W, you can use an overhead moveable track, known as a light mover, to move your light back and forth to create more uniform growth. These systems are worth investigating for high value hydroponic crops because a more uniform lighting pattern can help optimise yield.
This article provides a list of frequently asked questions with a brief answer to act as a problem solving document to help you overcome general grow room and plant problems.
Roots zone, tank and growing media 1 - The plants roots are not growing out their rockwool cubes – Most likely cause is that the plant has not been established well enough before planting. This is then followed by over-watering which creates poor root growth. This is a very common problem with NFT growers.
2 - My roots have turned an off white/beige colour – Normally due to over watering. Can also happen when the plant has become deficient in a nutrient through either the pH being out of range or excessive heat coupled with low humidity. Calcium deficient plants often have discoloured roots. Sometimes it can be a pre-cursor to the onset of a root disease, but this is less likely. Some additives contain ingredients that stain or discolour roots - e.g. humates.
3 - My Plants roots are brown/smelly/mushy – These are the signs of the latter stages of a root rot disease most likely to be Pythium. Once you have a root disease it cannot be cured. In extreme cases of over watering this will also happen.
4 - I have a green slime on roots/growing media – This is algae which grows on damp surfaces in the presence of light and nutrients. It is relatively harmless if kept to a minimum, but it needs managing. The first step would be to stopping light entry by covering the affected surface. Hydrogen peroxide will kill algae and quickly clear it up.
5 - I can see worms/maggots around the roots - If they have a clear body with a black head, they are sciarid fly larvae which eat your roots. You will also normally see small black flies around the base of the plant which will be laying eggs. Deal with these by using sticky traps to catch the adults and fungus gnat off to kill the larvae.
6 - Small black flies around surface of growing media/roots – Sciarid flies, see 5
7 - There are jumping insects on the surface of the water/growing media – These are harmless insects called ‘springtails’. Treatment is unnecessary.
8 - There is an oily look to surface of nutrient solution – This is calcium nitrate in high concentration in the solution. Relatively harmless if the tank is changed regularly.
9 - My pH is decreasing during early flower – This is quite normal nutrient uptake for a plant that is undergoing a developmental change from vegetative growth in generative (flowering) growth. Adjust back up to keep in range using silicon or ph Up (potassium hydroxide) and no problems will occur.
10 - My pH is decreasing rapidly – This could be a fungal infection; either a root rot disease or even botrytis.
11 - The nutrient strength (CF/EC) is increasing rapidly – This is commonly due to the plant undergoing high levels of transpiration caused by low humidity and/or high temperatures. Just add water to bring the nutrient strength back to desired level. If using a growing media check for salt build up and consider flushing.
12 - My nutrient strength (CF/EC) is decreasing – Caused by plants with high nutrient demand. Can come about when hydroponic systems are working to their optimum level. Add more nutrient to bring up to the desired level
13 - There is a sludge or snot like substance in/on nutrient solution – This is caused by beneficial bacteria and enzymes in the solution proliferating. Can happen when additives containing bacteria are overused or when different additives are mixed. Sometimes this problem can be due to algae (see 4).
14 - There is a slime-like substance on pipes in nutrient tank – See 13
Plants and leaves 1 - All the leaves are limp and wilting – most commonly due to under watering, but can also be cause by over watering. If temperatures are too high (above 30ºC) and/or the humidity is too low (below 40%) wilting will also occur.
2 - All the leaves are going an even pale green/yellow on my young plants – normally caused by under feeding, start feeding or increase the nutrient strength.
3 - The leaves are going an even pale green/yellow on my mature plants – If this happens in the first few weeks of flowering and is usually a sign of over feeding in which case you should decrease the nutrient strength. This can also be underfeeding if in late vegetative or mid flowering stages- see 2 and 7
4 - My leaves are going yellow but the leaf veins are still green – This is caused by a (magnesium) Mg deficiency if it’s on the older mature leaves. To correct foliar spray with Epsom salt solution (1 teaspoon to 1 litre) If its only on the new younger leaves it is an Iron (Fe) deficiency which is normally caused by high pH of nutrient solution.
5 - The leaves are turning a purple colour- Most commonly cause by low temperatures and often happens in winter or with outdoor grown plants. Can also be a phosphorus deficiency but this is less common.
6 - My leaves are very dark green and brittle/leathery – a classic symptom of over feeding. Reduce the nutrient strength.
7 - My Leaves are pale green and very soft velvety – usually a sign that you are underfeeding you plant. Increase the nutrient strength.
8 - A few top leaves have very pale/burnt patches on them – Usually caused by the lights being too close and burning the leaf tissue.
9 - The leaf tips are curling under- most commonly a sign of over feeding. See also 6 and 10
10 - The Leaf tips appear burnt – classic sign of over feeding, (see 6 and 9)
11 - The Leaf margins/edges are rolling up – when the leaves do this they start to look like tubes and is a sign that they are trying to stop water loss. This mean that the humidity may be to low, the lights are too close, the temperature is to high or there is too much air movement around the plants (wind burn).
12 - My leaves are distorted/curly/mutated but not burnt – can be a sign of Calcium (Ca) deficiency, also see 14
13 - The leaf stems are turning red–This can be a variety of minor issues that you should not worry about. Most commonly it is a stress response, happens allot when plants have not been hardened off properly. Can be cause by night and day temperatures being to far apart. Some plant varieties will always have red stems. It can also be a sign of under feeding if it occurs during aggressive growth stages.
14 - I can see orange-brown rusty spots with dark outline on the older leaves between veins and on leaf edges – Classic sign of Calcium deficiency which can be caused by prolonged periods of high or low humidity, very common in soil and coco. To correct spray with calcium rich foliar spray.
15 - There are rusty patches spreading up the plant – can be over feeding (see 6,9 and 10) or calcium deficiency (see 14)
16 - My leaves have random brown patches/blotches on leaves – If the patches/spots do not have a dark outline (see14) then could be a leaf spot fungus. Treatment is difficult but can be achieved through spraying or sulphur vaporisation. Cultural and environmental practices should be addressed.
17 - There is slug like silvery marks on my leaves – caused by plant eating insects called thrips. Check on underside of leaves for larvae (see 19), Control can be achieved through spraying and/or the predators.
18 - There are loads of white/yellow dots on the leaves – caused by spider mites check for small insects on underside of affected leaves. Control can be achieved through spraying and/or predators.
19 - Small worms/maggots on leaves – thrips larvae see 17
20 - I have water drops on leaves edges – Usually noticed when light just come on. Happens after dark period when growing media is wet and humidity is high which causes water to leak out of leaf edges (process is called guttation). Can also happen when growing media is wet and humidity drops when the lights go out. When leaves overlap each other water can also collect on the lower leaf.
21 - There is a white powder/dots growing on the leaf surface – this is a fungal infection called powdery mildew. Increase ventilation and air movement and use a spray with activity against fungus.
22 - My plants stunted plants with no growth and the leaves appear wilted – These are the symptoms of a vascular plants disease called Fusarium. Plants will not recover, confirmation can be obtained when the stem is cut in cross section and a brown ring is visible.
22 - Leaves on the plant are drying, the edges are burning and the stems are woody – Symptoms of wind burn which is caused when too much air is moving around the plants. Happen if you point a strong fan at a plant, always point circulation fans away from plants and towards the walls of the room.
23 - The Flower tops are stretching out – this happen when flower sets get heat stressed, usually remedied by raising lights or using a heat shield. Can also happen if the dark cycle interrupted, never go in your room when the light are off.
24 - The leaflets around flowers are turning yellow– Usually a sign of a botrytis/bud rot infection. Gently open the flower set to see if grey mould is visible. Remove any infected flowers immediately, treat other plants with a spray with activity against fungus .
25 - I can see fury grey fuzz/mould in flowers – botrytis/bud rot infection (see 24)
26 - My Flower sets are stretching/airy not dense – Most likely that the plant is not receiving enough fresh air (Co2). Can also be heat stress related (see23) and also under feeding.
27 - My plants won’t flower and have stretched and elongated stems– Happens if the light cycle is interrupted during dark period, never go in your room when the lights are off, check for any bright L.E.D’s on equipment inside your room.
28 - My plants seem too big and leggy – very common in summer, happens when temperatures are too high. Can be a sign of not enough light but very uncommon. Some plants are naturally big and tall which are unsuited for indoor growing.
29 - The plants are stunted/stopped growing and the leaves discoloured – possible disease, normally associated with Pythium (see Roots section, 3)
Cuttings and Seedlings 1 - My Cuttings won’t root – This is a very common question and can be due to a number of factors.
The most common is the growing media you are using is being kept too wet. If you are using rockwool, after pre-soaking shake the cube to expel the excess water within the cube. When you spray your cuttings spray the foliage lightly not the cubes. Never leave water standing in the bottom of the propagator.
Cuttings will take a long time to root if they are too big, try to take smaller cuttings around 3” (7-8cm) and remove big leaves from the cuttings to reduce leaf surface area.
Check you rooting hormone is still in date Do not use strong nutrients to pre soak cubes with as this will inhibit root formation. Make sure the temperature is between 18-24ºC and is kept fairly constant. If your temperature falls more than 4ºC between day and night keep you lights on continuously to maintain a constant temperature. Make sure you use a propagator and the vents are closed until roots appear. Be patient, the average time to root cuttings is 10-14 days.
2 - My cuttings are wilting – Can happen soon after taking the cutting but they should come back around. If they stay wilted its usually a sign temperatures are too high (common problem in summer months). Reduce temperatures in the propagation area.
3 - The base of the stem on seedlings/cuttings brown/black/rotting – This happens when the growing media is kept too wet which invites fungal diseases to attack the plant collectively know as ‘damping off’ diseases. This is particularly problematic in warm and wet conditions.
1 - I’m experiencing over feeding problems but nutrient is within range – the first thing to do in this situation is to calibrate your pH/CF meters as they could be giving you incorrect readings. It could be a nutrient salt build up in the growing media in which case you will need to flush your growing media. If your temperatures are high and humidity is low you plants will have a high transpiration rate which will cause them use more water and less nutrient which will cause a salt build up to happen. You could be suffering from wind burn which can look like nutrient burn.
2 - My Yield has gone down – The hardest thing in horticulture is to replicate consistent results and there are so many variables. The first thing to consider is that are all variables the same?
Plants variety is the obvious variable that can considerably change yields.
The environmental conditions are very important and will nearly always differ between crops (max-min temps and RH).
HPS Lamps need replacing every 9-12 months to maintain good light output and over time yields will go down if lamps are used for too long.
More is not always better so address the amount of nutrient you are using and the amount of additives that are being used or overused. Equipment Problems 1 - My light keeps blowing timers – All H.I.D lighting units that run high pressure sodium or metal halide lamps draw a lot of power when they start up so cannot plugged straight into a timer. You need to use a contact relay which will start you lights up without drawing a large inductive load through the timer.
2 - My ballast is making a loud buzzing noise – make sure bulb is screwed in fully and i.e.c connectors are pushed tight together, if unit is old consider replacing.
3 - The pump is on, vibrating but not pumping any water – this mean that the pump is either air locked or the filter is blocked. If your submersible pump is air locked you will see a group of air bubbles leave the pump when to turn it upside down under water. If your pump has an internal filter (micro-jet pumps that come with the nft gro-tanks) then they need cleaning every few weeks by rinsing in clean water.
4 - Smell is leaking out of my grow room – This happens when you room has a positive air pressure created when you have more air coming through your intake fan than being removed through the exhaust. To combat this you need to decrease intake and increase your extraction. Remember: if you use a carbon filter it will reduce the efficiency of your fan by up to 25%.
5 - My drippers keep clogging up – This normally only happens when the additives being used (beneficial bacteria, enzymes, silicon,) are causing a salt build up or bio sludge to block the dripper outlets. It is more common in hard water areas where carbonates in the water will calcify on the drippers. Using Canna d-block will help prevent sat build up on drippers. Some dripper blockages are caused when there is not enough pressure in the drip lines so consider upgrading the pump.
6 - My ventilation system is too noisy– Fist thing you need to establish is where the noise is coming from. If it’s the fan motor then all you can do is add padding around it or make and insulated box for it or upgrade to an acoustic fan. Most noisy ventilation systems are caused by the movement of high volumes of air through ducting which can be reduced by making sure ducting is straight and smooth. Consider acoustic ducting or using a fan speed controller to slow fan down
7 - My carbon filter is not working – This happens when the humidity runs too high, above 75% the activated carbon will not be work effectively. Remember that most activated carbon has a life span that ranges between 6 to 18 months so if it has been in use for a while and has stopped working then it may need replacing. Also (see 4).
You want to build your very own grow room, but don’t really know where to start. Like others new to soil-less gardening, you may be confused by the jargon that is sometimes associated with hydroponics. Well, if so, this article is perfect for you. With the jargon kept to a minimum, it will help you to establish a better understanding of indoor growing.
When planning your grow room you must ensure:
You have access to plenty of electricity - ask yourself whether there are enough plug sockets for your needs.
You have a good water supply - this will stop your plants dying of thirst
You can ventilate the area - make sure you have access to fresh air and can eject wasted air.
Remember, modifications which are made late can be very messy!
If a plant is unhealthy, it is usually a sign of poor air exchange. In fact, poor air exchange is the cause of at least 90% of growers problems that we diagnose and help rectify. Good air exchange will:
Extractor fans vary in size. As a rule of thumb, the more lights your grow room has the larger the extractor fan you’ll need.
Media based and non-media based hydroponic systems usually contain little or no nutrients. Essential minerals, which all plants need, must therefore be supplied by you, the grower, in the form of a nutrient solution.
Nutrient solutions vary in strength. The strength of nutrient a plant requires will depend upon the type of plant and its growth stage. You can add nutrients to your reservoir based on the volume of water it holds. For more accurate control we would recommend measuring the strength of the solution with a conductivity meter, which will give you a reading of the Conductivity Factor (CF) or Electrical Conductivity (EC) of the solution. The higher the number, the stronger the nutrient solution.
The pH factor is also important as it determines how easily a plant can absorb the nutrients available in a solution. The quicker a plant can absorb the nutrients, the faster it’ll grow. A pH measure of 0-6 indicates a solution is acidic, 7 is neutral, while a reading of 8-14 will mean it’s alkaline. Most plants prefer a pH range of 5.5 to 6.5. You can test the pH using a basic pH kit.
You should test and adjust the CF and pH every day to suit your plants’ requirements.
Lighting intensity and spectral output:
Light is the one of the most important environmental factors - without it a plant can’t survive. Remember, for a plant, light is basically food. Most indoor gardeners use artificial lighting to increase growth rates and achieve bumper yields. You should place artificial lights directly above your plants.
Tip – Remember, increasing the amount of light increases heat. Don’t let your room temperature exceed 30ºC as this will actually reduce yields!
Planning the crop involves:
Tip - If you’re new to soil-less gardening, we recommend starting with Nutrient Film Technique (NFT) growing systems.
In brief: Now you should be well on your way to building your very own indoor garden. But remember to:
Propagation Propagation is simply the creation of new plants. Many growers propagate using hydroponic techniques to benefit from early rooting and faster growth rates. This is possible because hydroponic growing media provides the root zone with easy access to water, nutrient and oxygen.
Propagation: Seed vs. cuttings Firstly, as with any type of propagation, you need to decide whether you want to grow from seeds or cuttings. Generally, growers who propagate from seed do so because it gives them peace of mind that their plants will be disease and pest free. However, the main draw back with seeds is that the characteristics of plants you produce can be inconsistent. Whereas, with cuttings you are producing plants that are identical to their healthy parent, this is why cuttings are also referred to as ‘clones’. Other advantages of cuttings include:
Earlier flowering. Improved plant stock. Plant species which are more adaptable to climatic variations. As growing from cuttings has so many benefits, at Aquaculture, we usually recommend our customers to use this method of propagation. However, for your first gardening venture you will probably have to start growing from seed. Our document ‘Germinating your seeds’ should be of help. It is advisable to germinate several seeds at the same time. You will then be able to choose a mother (stock) plant from which you can take cuttings in future.
Taking cuttings Setting up – You will need the following items:
Propagation cubes/plugs. Rooting hormone. Heated or unheated propagator Fluorescent lighting. Sterile scalpel. Spray bottle. Nutrient. Rooting stimulator. This article explains how to propagate using rockwool cubes. However, the process is basically the same for all types of propagation, such as ROOT!T Rooting Sponges and Jiffy-7’s.
The Mother Plant You will have to grow your seedlings or cuttings under 18 hours of light until they are suitable to take cuttings from. This is usually when they are between 12-18 inches or have 8-10 internodes.
Label your seedlings with numbers or names so you can label your cuttings you take to correspond with the parent plant.
When your seedlings are ready, trigger them to flower by giving them 12 hours of light and 12 hours of darkness. Take the seedlings to full maturity to determine which shows favourable characteristics, i.e: quickest to root and/or best flower development.
While your plants are flowering, the cuttings will need to be kept in a vegetative state in a separate growing area with 18 hours of light and 6 hours of darkness.
The cutting with the same name/number as the plant with the most favourable characteristics should be kept as the mother plant.
Mother Plants can be grown in a variety of systems. We would recommend choosing a media based growing system as you will typically keep the plants for up to a year. Systems using techniques like NFT, bubblers (deep water culture) and aeroponics are more suited to short term crops.
The most popular method of keeping mother plants is using soil, or soil-less growing media in pots, which can be watered by hand or via and automatic delivery system.
Quality of cuttings If you want strong healthy cuttings, it is important to consider the quality of the mother plant they are coming from. Make sure the mother plant is regularly trimmed to promote lots of side branches. This will give you more sites to take cuttings from. It is also advisable not to feed your mother plant too much. Overfed plants will produce thicker stemmed ‘woodier’ branches and cuttings that will take longer to root.
The highest concentration of growth is concentrated around the bottom 1/3rd of the plant around the inner shoots. This is where you should take your cuttings from. Growers often refer to this section of the plant as the ‘zone of juvenility’.
Without stripping more than 25% of the foliage, take as many cuttings from the mother plant as possible. Also, it is preferable to use cuttings which have a few leaves. Cuttings with large leaves tend to be unable to absorb sufficient water through their stem. Those with thinner stems will also root much faster than cuttings with fatter stems.
Fluorescent lighting As stated above, seedlings/mothers need to be grown under 18 hours of fluorescent light and 6 hours dark. However, once they are well rooted, you will need to switch to 12 hours of HID light and 12 hours of dark to initiate flowering/fruiting.
In the first week, before the roots have formed, cuttings will perform best with the fluorescent lighting unit positioned 25-50cm away from the propagator lid. When using HID lights for propagation you should only consider using 250w metal halide lamps. These should be positioned 1m away from your propagator. Higher wattage HID lamps will emit too much light and heat, and may result in your cuttings failing to root.
Rockwool propagation cubes The main advantage of rockwool is that it holds more air and water than any other growing medium. Rockwool is also inert and sterile, and does not hold onto nutrient in any way. The roots are clearly visible and it is very easy to tell whether the cubes are moist or dry. They can be transplanted into larger rockwool blocks or any other hydroponic media with the minimum of fuss. Cuttings should take approximately 7-14 days to root. At this stage, you will need to transfer your cuttings into larger rockwool cubes or your chosen hydroponic growing medium.
A simple step by step guide to taking cuttings
Clean all work surfaces and equipment with a disinfectant.
Soak the rockwool cubes in a suitable nutrient solution for at least an hour. Shake the cubes to remove excess liquid. Plants need oxygen to root; rockwool which is too wet can prevent rooting and encourage disease.
As highlighted above, you should take cuttings from the base of the plant, around the outer shoots. Choose shoots which have 3-4 sets of leaves. With a smooth motion, cut at a 45 degree angle just below the internode (branch/stem join).
Immediately immerse the cut stems into a bowl of tepid water.
Remove the bottom leaves from the stem. Also, if the cutting has more than one large fan leaf, remove the extra.
With the scalpel, gently scrape the lower part of the stem. This will help initiate faster rooting.
Apply the rooting hormone to the cut stem or cube, as directed on the product packaging.
Gently insert the cutting into the cube. Lightly pinch the cube to hold the cutting in place. After all the cuttings are inserted into the cubes, place them back in their plastic tray and position in a propagator. Finely mist the cuttings with water, and then place the propagator lid on the tray. Place the fluorescent lights over the propagator. Give your cuttings 18 hours of light a day. However, if the air temperature drops by more than 4ºC when the light goes out, leave the lights on continuously. Once a day remove the propagator lid and finely mist the propagator lid. Roots should appear within 7-14 days. Once this is evident, the propagator vents can be opened. If you wish to transplant the propagation cubes into larger rockwool blocks, simply pre-soak the blocks with a suitable nutrient and a rooting stimulator. As with the cubes, it’s important that the rockwool blocks are not too wet. Insert the cubes into the larger blocks and place them onto a plastic tray or a surface on which the plants can be ‘air pruned’ (see below). Roots should appear on the bottom of the blocks within 2-7 days. After 10-14 days there should be loads of roots on the bottom of the blocks, at this point you can plant into your chosen hydroponic system. Do not be tempted to place your plants onto their system too early, only when there are an abundance of roots on the bottom of the blocks should you consider planting on. Air Pruning This is a propagation technique used to help promote a healthy root system. It involves placing your plants in rockwool blocks on a perforated tray or wire mesh. This should be positioned so air can naturally flow underneath the blocks. With this technique as the root tip grows out of the blocks it detects the dry air and dies back. This forces the root, still within the block, to branch out forming more roots. This means the roots concentrate their growth within the block. Eventually you will have a plant with loads of small root tips protruding from the block with a large mass of roots within the block. Soon after the plant is put onto its final system the roots extend from the block very quickly, getting the plant off to a great start. This technique is particularly useful for NFT although should be employed for all types of systems.
Using Heated Propagators If your propagation area is too cold your cuttings and seedlings will take a long time to establish. If you have temperatures below 18ºC inside you propagator you will need to use a heating mat or warming pad underneath your propagator, or buy a new heated propagator. When using heat from a mat, pad or heated propagator it is recommended you use a 2.5cm layer of perlite or vermiculite, or a mixture of both, in you propagator tray. This will help spread the heat throughout your propagator avoiding ‘hot spot’ areas.
Using ‘Aeroponic’ Propagators Recent advances in propagation equipment has led the UK’s leading systems manufacturer ‘Nutriculture’ to make available an affordable compact range of systems for propagating cuttings using aeroponics. With aeroponic propagation there is no need for any growing media, the main stem of the cutting is clamped in a sponge collar which is inserted into a net pot. This net pot is placed in the system where the stem gets a mist continuously sprayed around it. This promotes the ideal air to water ratio and cuttings often root within 5 days.
Once there are roots on the cutting you can transplant into a pot containing growing media. If you want to transplant into a large rockwool cube you can buy the large hole variations of the 3” and 4” blocks and fill in the space with perlite, vermiculite, coco coir or small clay pebbles. It is also possible to use small clay pebbles in the net pot, then place in your un-rooted cutting and place in the aeroponic propagator. The roots will still grow out quickly and the net pot can be placed straight into a Grodan 3” or 4” transplant block.
Troubleshooting/FAQ’s: Q. My Cuttings won’t root
A. This is a very common question and can be due to a number of factors.
The most common is the growing media you are using is being kept too wet. If you are using rockwool, after pre-soaking shake the cube to expel the excess water within the cube. When you spray your cuttings spray the foliage lightly not the cubes. Never leave water standing in the bottom of the propagator.
Cuttings will take a long time to root if they are too big. Try to take smaller cuttings around 3” (7-8cm) and remove the big leaves from the cuttings to reduce leaf surface area.
Check your rooting hormone is still in date. Do not use strong nutrients to pre-soak cubes with, as this will inhibit root formation. Make sure the temperature is between 18-24ºC and is kept fairly constant. If your temperature falls more than 4ºC between day and night, keep your lights on continuously to maintain a constant temperature. Make sure you use a propagator and the vents are closed until roots appear. Be patient, the average time to root cuttings is 7-14 days.
Q. My cuttings are wilting
A. This can happen soon after taking the cuttings but they should come back around. If they stay wilted it’s usually a sign that temperatures are too high (common problem in summer months). Reduce temperatures in the propagation area.
Q. The base of the stem on seedlings/cuttings brown/black/rotting
A. This happens when the growing media is kept too wet which invites fungal diseases to attack the plant, collectively know as ‘damping off’ diseases. This is particularly problematic in warm and wet conditions.
In your mission to achieve the best possible results, producing strong and healthy cuttings or seedlings is absolutely essential. This is because the condition of your young plants will be reflected throughout the remainder of their life cycle. The stronger they are during the vegetative period. This maximizes the plant's potential through flowering.
Media At Aquaculture we supply a variety of quality media for you to successfully begin propagating. Regardless of the media you choose to begin with, you will always be free to transfer and plant into another form of media should you choose to.
Media Recommended Rooting Compound Benefits Points to Consider
Fast rooting times and popular for rooting when transplanting to larger rockwool blocks
Be careful not to over or under water
Jiffy - Coco
Clonex/ROOT!T Rooting Gel
Easy to use - won’t dry out as quickly as rockwool cubes and don’t need to soak as long to prepare.
Slightly slower to root than rockwool /aeroponics.
ROOT!T - Rockwool Blocks
ROOT!T Rooting Gel
Fast rooting times and popular for rooting when transplanting to larger rockwool blocks
Be careful not to over/under water. ROOT!T - Coir & Peat Pellets
ROOT!T Rooting Gel
Easy to use - won’t dry out as quickly as rockwool cubes and don’t need to soak as long to prepare.
They are slightly slower to root than rockwool /aeroponics. There is also no cloth at bottom of cube (resulting in messy preparation).
Fleximix - ROOT!T Cubes
ROOT!T Rooting Gel
Easy to use – quick rooting times and come ready to use in handy propagation kits.
Can dry out quickly and easily Aeroponics
VitaLink Bioplus in water (or halfstrength VitaLink PlantStart)
Very quick rooting times and no media is needed.
Transferring to other media could induce higher transplant shock.
Rockwool Cubes and ROOT!T Rockwool Cubes - soak for 4-5 hours in a solution of 2ml/L of VitaLink Bioplus, and 3ml/L of VitaLink PlantStart at a pH of roughly 5.5-6.0. Finally, gently squeeze or flick off any excess water. Jiffy Soil and ROOT!T Coir/Peat Pellets - soak for 10 mins in solution of 2ml/L of VitaLink Bioplus at a pH of roughly 6.0. Finally, gently squeeze or flick off any excess water. Jiffy Coco - soak for 10 mins in solution of 2ml/L of VitaLink Bioplus, and 3ml/L VitaLink PlantStart at a pH of 5.5-6.0. Finally, gently squeeze or flick off any excess water. Flexicubes and ROOT!T Cubes - Optional. If you do choose to soak, use a solution of 2ml/L of VitaLink BioPlus and 3ml/L of VitaLink PlantStart at a pH of roughly 5.5 - 6.0. Finally, gently squeeze or flick off any excess water. Feeding guidelines: For all the above media, soak for 4-5 hours in a solution of 2ml/L of VitaLink Bioplus, and 3ml/L of VitaLink PlantStart at a pH of roughly 5.5-6.0. Finally, gently squeeze or flick off any excess water. However for aeroponics media, simply keep the tank topped up with a solution of 2ml/L of VitaLink Bioplus and 3ml/L of VitaLInk PlantStart. *Please note: Do not over water your cuttings. They like to be moist, not wet!
Propagators Once you have determined the media you would like to root into, you then need to decide on the most appropriate propagator to match your requirements. The following table exhibits the range of propagators we offer which are all tailored to your budget; ensuring you get the most value for your money.
Propagators Overview ROOT!T Fleximix Propagator
Comes with Fleximix blocks, scalpel and an instructions kit for almost everything you will need to take perfect cuttings. (Sizes – small)
ROOT!T Budget Propagator
Its large size enables it to hold a full tray of 77 Grodan 1.5” cubes. (Sizes – large)
A customisable propagation unit, allowing you to increase the height and size of your nursery area to suit your needs. Available in both heated and unheated varieties. (Size - customisable)
Stewart Un-heated Propagators
Very reliable and an ideal choice if you’re running on a tight budget. (Sizes – small and large)
Stewart Heated Propagators (2 versions – Variable and Heat & Grow)
Excellent for heating root zones to promote quicker rooting times. The Heat & Grow is a more affordable ‘plug and go’ propagator, whereas the Variable stands at a more premium price with its added ability to give greater control over the heat applied. (Sizes – small and large)
Very large propagation units that can house up to 3 trays of 1.5” Grodan cubes, and achieve a high output of cuttings. Lids can be purchased separately for makeshift propagation areas. (Sizes – extra large)
Regarded by many to be the ultimate way of taking cuttings quickly, easily and efficiently. There is no need for any media to root into, very little maintenance is required and the nature of the unit creates constant levels of adequate humidity for the cuttings. (Sizes – Small, medium, large and extra large)
Hint – If you are propagating or ‘hardening off’/‘growing plants on’, it is more cost effective to heat the root zone with a BioGreen Heated Propagation Mat than it is to warm the whole growing area with a grow room heater.
Lighting In order to root cuttings or raise seedlings effectively, you must provide them with the required lighting. This means using a specific propagation light that will provide constant gentle light and heat, as opposed to the HID lighting used for vegetative and flowering stages (which is generally too strong for fragile young plants). So whether you’re producing hundreds of plants or raising a few seeds or cuttings, our range of lighting will meet all of your propagation needs and budget!
Light Overview/Benefits Sunmate Grow (150W or 250W) Sunmate Grow Twin (150W or 250W)
150W bulbs are ideal for cuttings and seedlings, whilst the 250Ws are also suitable for early vegetative growth. Available in a range of spectrums to suit your specific lighting requirements - Warm (red), Cool (blue) and Super Cool (blue/white).
Cool (blue/white). T5 Budget Sunmate Grow Twin(150W or 250W)
These high output propagation lights enable you to ‘daisy chain’ up to 8 of these from a single plug. (Available in 2” or 4” versions)
T5 Lightwaves 2” and T5 Lightwaves 4”
Utilize the same high output bulbs as the budget lights, and are fitted into a high quality reflector to provide the best spread of light possible. The 2” comes in either 2 tube (48W) or 4 tube (96W) and the 4” comes in 4 tube (216W) or 8 Tube (432W). The 4” version is perfect for larger propagators such as the X-stream.
A small, convenient and low power consumption bulb. These are good to use over smaller propagators. (Available in 2 bulbs - each being 55W)
Relative humidity (RH) is often overlooked when growing indoors. However, if you want strong healthy plants, you need to consider the relative humidity of your grow room. Here we explain what you need to know....
What is RH and why is it important? RH is the amount of water vapour in the air compared to how much moisture the air could possibly hold at that temperature. Plant growth is influenced by RH because it directly affects the amount of water your plants move through their stems and leaves - essential for keeping plants hydrated and transporting vital nutrients.
What should the level of RH be in my grow room? For healthy plant growth, you should aim for RH of 50-70% (RH can be measured using a hygrometer).
What are the consequences if the RH in my grow room is too high? When RH levels are too high in your grow room, you have the perfect environment for spores to germinate and fungi to grow. The most common type of mould you will encounter is Botrytis (bud rot). Others include leaf moulds, such as Powdery Mildew. There is also a risk of stem infections, although these are less common.
Hint: a lack of adequate ventilation can often be a cause for excessive RH. Please refer to our ventliation article for information on how to solve such problems. If ventilation is not an issue, a quick and easy way to lower humidity is to use a dehumidifier. An air conditioning unit during the summer that expels cool, dry air, will also help reduce RH.
What are the consequences if the RH in my grow room is too low? When your grow room is suffering from low amounts of RH, the leaves of your plants begin to curl upwards at the margins; looking like a tube/straw. The low RH decreases the amount of transpiration as less leaf surface is exposed to dry air, which lowers the amount of water your plants will lose.
Generally, low RH tends to be more common than high RH. In fact, when growing indoors under hot lights, most hydroponic growers tend to start off with very low RH. This is problematic because RH needs to be relatively high during the vegetative growth stages.
Example of a low humidity problem: When you start out, your plants will be small with not much vegetation. The grow light(s) will also heat and dry the air in the grow room; giving a RH level of 35-50% and temperature of 25-28°C. This will cause the small plants to take up and release increased amounts of water to balance water vapour in the air. This stresses the plants considerably by taking away the energy it needs to produce new roots, shoots and leaves. But if you increase the RH levels up to 60-70% during these vital, early stages, you will ensure quicker establishment of roots, vigorous growth and compact internodes. Ultimately, your plants will grow faster and healthier.
Once the plants have grown in size and have produced more shoots and leaves, they will take up more water into their roots and lose more water vapour from their leaves. As there is more water vapour being released into the air by the plant, the humidifier can now be switched off.
If the RH in your grow room falls back below 40%, you will experience a lot of problems - one of them being over-fertilisation. High temperatures and low RH will cause your plants to take up and release more water. Whilst your plants are taking up more water, they will take up less nutrient - causing the nutrient to continually increase in strength. It is this increase in nutrient strength - coupled with an increase in water uptake and release - that causes over-fertilisation of your plants and other nutrient related problems.
The link between RH and temperature is the cause of many problems during the summer months, but despite this, it is still one of the first things that is overlooked.
Humidity and the Dark Cycle Some indoor growers find that when the lights go out, RH shoots up. This leads to mould problems like Botrytis on fruits or flowers if the night time humidity is too high. This can be corrected by using a dehumidifier. Be sure that the dehumidifier does not remove too much water during this time, as it can over-dry the air; causing the plant to lose water through its leaf tips. This water can then collect on the leaves, creating the perfect micro environment for spore germination. Ideally, you want your grow room to have a lower humidity during the day compared to the night. The ideal figures to aim at during fruit/flower formation would be 50-60% in the light cycle, and 60-70% during the dark cycle.
Humidity and Propagation During the propagation stages (rooting cuttings or germinating seedlings) RH is controlled and kept high using a propagator - such as the Stewart Heat and Grow Electric propagator. We recommended that you spray the lid of your propagator daily to keep the humidity above 80%. This will minimise water loss through the plant and concentrate its energy on producing new roots.
In summary, you will achieve the best results with your plants if you keep humidity above 50% and below 70%, and ensure RH is not lower in the night than day.
Overlooked by many growers, carbon dioxide is vital for healthy plant growth. In fact, maintaining optimum levels of Carbon dioxide can significantly improve the yield of your plants. Read on to learn how you can use Carbon dioxide to get the best results from your plants.
What is carbon dioxide and how is it measured? Carbon dioxide is a natural gas present in our atmosphere. It is measured in parts per million (ppm). In the atmosphere there is about 300 - 400ppm of carbon dioxide.
Why is carbon dioxide so important? Without carbon dioxide your plants will not grow. This is because it is essential for photosynthesis – the process by which your plants use light, water, and carbon dioxide to make glucose (plant food). Your plants need glucose for healthy growth.
Photosynthesis can only take place in the light period. This is when the leaves of your plants absorb carbon dioxide and give out oxygen. During the hours of darkness, the leaves give off carbon dioxide and absorb oxygen.
During higher temperatures and light levels, the absorption of carbon dioxide and the rate of photosynthesis will also increase until a maximum is reached. Most growers are aware that optimum light and temperature can enhance plant growth (you may want to refer to our ‘Lighting’ and ‘Temperature’ articles). However, even if optimum light and temperature are achieved, a lack of carbon dioxide can be a limiting factor – which means you will not get the best results from your plants.
It is important to be aware that if temperature exceeds 32ºC, the stomata (breathing holes) of your plants will close. Consequently, your plants will not absorb carbon dioxide, which means they will not grow. Like most growers, you will probably be using an extractor fan or a cooling system to keep the temperature at an optimum. If so, you will need to switch the extractor/cooling system off whilst adding the carbon dioxide to prevent it from being extracted before your plants absorb it. This will have an influence on injection times, which is explained towards the end of the article.
Carbon Dioxide in my grow room As mentioned, there is approximately 300-400ppm of carbon dioxide in the atmosphere. However, whatever carbon dioxide that is present, will not last long in a tight grow room with little to no ventilation. A lack of carbon dioxide will prevent your plants from photosynthesising, and eventually stop growing. To avoid such a situation, you need to ensure that there is an adequate amount of ventilation in your grow room (please refer to our ‘Ventilation’ article for more info).
It is possible to speed up the photosynthesis process by increasing the level of carbon dioxide to 1000-2000ppm during the light period. This will enhance the overall development and yield of your plants.
Tip- If you are adding carbon dioxide to your grow room, always use an oscillating fan to ensure it is well mixed.
How do I know how much carbon dioxide I need to give my plants? When adding carbon dioxide, you need to consider the size of your grow room. The simple calculation/example below will help you to decide how much carbon dioxide to add to your grow room.
Length (m) x Width (m) x Height (m) For example, 3m x 3m x 2.5m = 22.5m³
Background level (approx amount in atmosphere) of carbon dioxide = 350ppm Desired level = 1500ppm
Desired level – Background level = Enrichment level 1500-350 = 1150ppm (=0.000115)
Capacity of your grow room x Enrichment level = Volume of carbon dioxide to be added 22.5 x 0.00115 = 0.026m³
0.026x1000 = 26L This means that 26L of carbon dioxide is required per injection to raise it to the desired level.
The timed injection is up to you, however; shorter injection cycles are preferable to longer cycles.
For example, 26L of carbon dioxide means you would release 13L per minute for 2 minutes. You would then dose again 1-2 hours later.
Shorter injection cycles are better because carbon dioxide is available to your plants more often. It also means that you will not need to have your extractor fan/cooling system off for long periods of time.
Tip – There are controllers available with C0² sensors that monitor the growing environment to ensure there is an optimum amount of carbon dioxide in your grow room.
When should I add carbon dioxide? We would recommend that you start adding carbon dioxide as soon as you put your plants into your chosen hydroponic system. You should continue adding carbon dioxide up until harvest. Never suddenly remove the extra carbon dioxide you are supplying to your plants. This can have an adverse effect on your plants’ overall development.
We hope this information article has helped you to understand how important carbon dioxide is to your plants’ development and how you can use it to enhance their performance. If you require further advice, please do not hesitate to contact us.
When the temperature rises outside, so does your grow room temperatures with potentially damaging consequences. Flowers become loose, fruits can abort and yields can be significantly reduced. Maintenance of your grow room operation becomes more intense as the plants consume more water through transpiration to cool the leaf temperatures down. Nutrients become toxic because this increased transpiration drives nutrient uptake. The first symptom of toxicity usually leads to yellowing of the middle-aged to larger leaves just below the flowering tops. All this leads to growers looking miserable on hot, sunny days rather than enjoying it.
If you also want to inject with carbon dioxide, then the only efficient, controllable way to achieve this is to use air conditioning. In order to put a smile back on your face on those hot sunny days or indeed those cold cloudy days where you want to inject with carbon dioxide but you still cannot have the exhaust fans off for any length of time then Aquaculture is pleased to offer advice on using air conditioners.
To help you decide which cooling product best suits your needs, simply answer the following questions:
Permanent air conditioners that require professional installation are usually not suitable for grow rooms, but portable units are. There are 2 types of portable air conditioners, mono-blocks and portable split units.
Mono-blocks are an all in one unit that have an exhaust hose, air is pulled into the unit while cool air is blown out the top and hot waste air is blown out the exhaust hose. These can be used inside grow rooms, but if your crop has a strong odour this will also be blown out the exhaust hose. Mono-block air conditioners are best used outside grow rooms, this cooler air can then be pumped into the grow room via an inline fan.
Portable split air conditioners have an outside unit and an inside unit. The outside unit processes the air and pumps refrigerant to the inside unit which blows out cool air. The inside unit can be placed inside the grow room without the risk of odours being pumped out of the air conditioner.
How do I calculate my air conditioning requirements? Simple! - Grab a calculator and follow the simple instructions
Example: Room dimensions are 7.6m x 3.7m x 2.5m = 70.3 cubic metres. (Multiply by 175 = 11,810 Btu's)
The above calculations assume a grow room with no lighting or other heat sources.
For every lighting system, add the following Btu amount onto the above calculation.
In that volume I have 4 separate 600W sodium lighting systems.
Easy then, this is what we do:
From the above example, 22.5 cubic metres multiplied by 175 = 3940 Btu's Multiply 4 (no. of lights) by 1530 (cooling for 600W light) = 6120 Add 3940 to 6120 = 10060 Btu's of cooling. If you have a south(ish) facing grow room or an attic then multiply the total Btu requirement by 1.5. If you are in any doubt about your calculations our sales staff will be happy to talk you through.
Do Portable Air Conditioners require installation? The mono-block air conditioners do not need any special installation other than placing the exhaust in a suitable location to vent away the hot waste air – then just switch on!
For the portable split air conditioners, there is no exhaust hose. The ‘umbilical cord’ links the inside and outside units, and contains R407C cooling refrigerant. The umbilical cord comes attached and ready to use, if you need to detach the cord for installation you will need to re-gas the unit with refrigerant. Please note: different AC units are filled with different types of gas which can be damaging to the environment and to human health, any type of AC re-gassing should be done by a trained professional.
Are there any special requirements for the use of Portable Air Conditioning? Yes. Access to an open window, vent, external door or suspended ceiling is essential in order to position the outside unit for split AC units types, or duct the hot air exhaust from mono-block AC units.
The air conditioner needs to be positioned within reach of a 13-amp 230V socket and located in a manner to avoid any obstruction to the airflow.
Always ensure that the electrical supply to the unit is adequate and not limited by the other electrical consuming products in your grow room.
Where do I position my Air Conditioning Unit? You obviously do not want to position the air conditioner unit next to the extractor fan. We have included a little diagram below to help you decide on a suitable position. The air conditioner should be located at one end of the room, usually at the opposite end from the exhaust fan. If you are using an intake fan as well, the unit should be located close to this to achieve a greater cooling capacity.
Relative humidity is still the most commonly used measurement for grow room control, even though it is not a perfect indication of what the plants ‘feel’. Plants respond to the difference between humidity levels at the leaf stomata and the humidity levels of the surrounding air. At the same relative humidity levels, but at different temperatures, the transpiration demand for water from the leaves can double. Therefore, another kind of measurement, called Vapour Pressure Deficit is often used to measure plant/air moisture relationships. VPD is defined as the difference in the amount of water in the leaf (always assumed to be 100% RH) and the humidity of the outside air is the VPD. The higher the VPD, the greater the evaporation rate.
Role of Humidity The main plant mechanism for coping with humidity is the adjustment of the leaf stomata. Stomata open and close in response to vapour pressure deficit, opening wider as humidity increases. When humidity levels drop the stomata can close to about 50% to help guard against wilting. This also reduces the exchange of CO2, thereby affecting photosynthesis.
Transpiration - Plants can control their rate of water loss. Because the leaf stomata have an ability to limit transpiration rates, a doubling of the moisture deficit may result in only a 15% increase in the transpiration rate. However, when humidity levels are very high, the total uptake of minerals is reduced since plants are unable to evaporate enough water.
Photosynthesis - Humidity levels indirectly affect the rate of photosynthesis because CO2 is absorbed through the stomatal openings. At higher daytime humidity levels, the stomata are fully opened allowing more CO2 to be absorbed for photosynthesis.
Growth and Quality - Most grow room plants tend to grow better at higher relative humidity. However, mineral deficiencies, disease outbreaks, smaller root systems, and softer growth are possible consequences of excess humidity.
Quality Problems Due to Humidity Too Low- Dry Tip Burn, Wilting, Small Leaves, Stunted Plants, Spider Mites, Leaf Curl.
Too High- Oedema, Edge Burn (Guttation), Soft Growth, Mineral Deficiencies, Disease Outbreaks.
Customers are always asking me what is the ideal humidity? There is no right answer to that as it is linked to temperature and vice versa. The table below will guide you to the optimal environmental control. All figures marked as red are considered ideal. All figures marked in green, require active dehumidification. All figures marked in blue, require active humidification. If the table looks too confusing, try to ignore the values in the boxes as these only refer to the Vapour Pressure Deficit, which you need not to be concerned with.
A grow room has a relative humidity of 60% and a temperature of 23ºC, from the table below I obtain a red figure, this is considered ideal.
A grow room has a relative humidity of 90% and a temperature of 30ºC, from the table below I obtain a green figure, this requires active dehumidification
A grow room has a relative humidity of 50% and a temperature of 30ºC, from the table below I obtain a blue figure, this requires active humidification.
Table 1. Relative Humidity and Temperature Targets to Obtain Optimal Vapour Pressure Deficits Gram/m3* and millibars (mb). Please download the attachment to see the table in full
*Optimum range 3-7 grams/m3, 3.9-9.2 mb
The table above displays how temperature and humidity influence the water loss from the plant through transpiration. Transpiration also drives nutrient uptake, so the higher the transpiration rate the higher the uptake of nutrients. Some customers will also ask what is the ideal nutrient strength to run at for their particular crop? Again, this is linked to the environment, you will have probably noticed that on hot dry days the speed at which your plants consume water is considerable. You will have also noticed that the strength of the nutrient solution has increased also. High transpiration rates can drive nutrient uptake to such a limit that the nutrients start to become toxic to the plant. As the strength of the nutrient solution is also increasing then the plants find it more difficult to draw water from the solution to satisfy transpiration, if the plant cannot draw enough water then the stomata partially or completely close to limit water loss. This effect will slow photosynthesis and stress the plants even further as the plant has no way to cool the leaf temperatures down.
Maintaining an optimum growing environment is vital if you want fast healthy plant growth and maximum yield. The growing environment is largely concerned with three key factors: grow room temperature, relative humidity (RH) and nutrient temperature. An optimum growing environment can vary from plant to plant. However, there are set ‘parameters’ you should aim to achieve for each environmental factor. The information below details the negative effect a poor growing environment can have on your plants. It also provides advice on how you can achieve the optimum grow room parameters required for excellent plant results.
Grow Room Temperature 40°C
The rate of cell death increases, which leads to the quick deterioration and death of your plants.
Cells begin to die and the health of your plants decline.
Stomata start to shut and plants begin to wilt.
The most ideal room temperature for your plants. You will achieve excellent growth and maximum yield.
This cold temperature will turn both the stems and leaves purple and slow plant growth
Preventing or reducing high grow room temperature - Use a fan speed controller to create a steady flow of fresh air in your room. Your grow lights will also give out a lot of heat; we recommend the CoolShade and AeroWing reflectors to effectively reduce the heat your grow lights emit.
Preventing or increasing low grow room temperature - Use a grow room heater to increase the temperature. You can also have your heater automatically regulated by a thermostat, which will make sure desired levels of temperature are constantly maintained.
Hint: Our bestselling ETI Digital ThermoHygrometer provides an accurate reading of both your grow room temperature and RH, which gives you a greater understanding of what is happening in your grow room. This will allow you to take corrective action if there are any problems.
Relative Humidity (RH) 80% RH
There is a higher risk of mould and stem/root infections occurring. The effectiveness off carbon filters are also rapidly reduced.
Ideal for plants during the vegatitive stage. You can expect lots of leafy green growth.
Ideal for plants during the flowering stage. You can expect large, healthy flowers. The slightly lower RH also reduces the risk of mould/fungus.
Below 40% RH
Plants begin to wilt and the leaves begin to curl upwards from the edges. There is also a danger of 'over-fertilisation' Preventing or reducing high relative humidity (RH) - Increasing your extraction may help because this will remove heat and moisture, whilst drawing in cooler and drier air. We are also currently trying to source dehumidifiers, which will effectively decrease the level of humidity in your room.
Preventing and raising low relative humidity (RH) - Our Centrifugal Humidification System & Kits are designed to increase the amount of RH in your room and are very straightforward to set up. Included in the kits are the Faran Humidistats, which work to accurately control your humidifier and make sure the optimal levels of RH are always maintained.
Hint: Try to maintain a consistent grow room temperature and RH during both night and day. A drop in temperature may be unavoidable during your night cycle, but try to minimise this to 5°C. An extreme drop in temperature will slow down plant growth and reduce your yield.
Nutrient Temperature Above 25°C
A high temperature will starve your plants of oxyge; resulting in root death and greater risk of pathogens.
Perfect temperature for your nutrient solution. It will give the roots plenty of access to oxygen. This allows your plants to absorb all of the nutrients they need for best growth.
A cold temperature will limit the ability of your plant's roots to absorb water and minerals, leading to poor plant health.
Preventing or reducing high nutrient temperature - Excessive nutrient temperatures can easily be dealt with using a nutrient chiller, which will prevent your nutrient solution from heating up regardless of how hot your room gets.
Preventing or raising low nutrient temperature - NeWatt Nutrient Heaters will warm your solution up to the optimum level required for excellent plant results.
If you want strong, vigorous plants and maximum yield, a healthy root zone is a must! Read on to discover how looking after the roots of your plants can help you to get the best from your growing…
Why are the roots so important? The roots are responsible for absorbing water and nutrients that your plants need for healthy growth and development. Water and nutrients are pumped up to the leaves; which produce dissolved sugars and other substances that are pumped back down to the roots. These sugars supply the energy that roots need to grow. If any of the sugar is not used, the roots will store it as starch. The roots and their capacity to store starch determine how well a plant will grow and how much the plant will yield.
How can I tell if the roots of my plants are healthy? If the roots of your plants look crisp and white with plenty of root hairs, they are healthy and will absorb the maximum amount of nutrients and water. If the roots develop brown tips or general browning, the problem is usually a lack of oxygen, and infection is likely to follow.
How can I ensure that the roots of my plants are healthy? There are a number of factors that affect the health of roots:
Growing space - never grow in pots that are too small, because the roots of your plants will become overcrowded and circle in on themselves. This will adversely affect the amount of nutrients and water that the roots can absorb, reducing potential yield.
Oxygen - the roots use oxygen to convert sugar to energy and to transfer nutrients to other parts of your plants. The older parts of the roots towards the stem absorb oxygen and release carbon dioxide. It’s important not to keep this part of the root system constantly wet. The bottom section can be kept constantly wet, provided that the water is well oxygenated. There are a number of products on the market that will provide the roots of your plants with extra oxygen. The most popular being, air stones with an air pump. Hydrogen peroxide can also be used to make slight increases in dissolved oxygen, and it also kills pathogenic organisms in the root zone. However, hydrogen peroxide also kill beneficial organisms and is not always compatible with all growth enhances or root boosters.
Temperature - to encourage healthy root growth and function, you should try to keep the temperature around the roots of your plants constant and warm. The roots are very active in the dark period. Ideally, aim for a day and night temperature of 20 ºC. Roots in a warm dark period (20 ºC) develop much better than those in a cool dark period (15 ºC). Irrigation - the most important for plant growth. The less energy the roots use to absorb water and nutrients from their surrounding area, the more they can use to grow and transport nutrients through the plant. Ninety per cent of the water taken in by a healthy plant is transpired out through the leaves. If the roots are unable to extract water from their surroundings, your plants will struggle and may start wilt. Bacteria & Fungi - not all bacteria and fungi are detrimental to plant health. In fact, some are not only beneficial but essential! There are a number of nutrient additives and growth enhancers that contain beneficial bacteria and fungi that help to encourage plant growth and protect against disease. Give your plants the start they deserve! A lack of roots is the most common problem growers encounter when they come to transplant their plants into the growing system. To address this, a technique called ‘air pruning’ comes with our highest recommendation.
When a root grows out of a growing media into relatively dry air, its tip is dried and killed. Once this first root is pruned, many secondary roots develop to replace it. These are then air pruned and replaced by even more roots. Basically, air pruning trains a root system with a very large quantity of young vigorous roots. The result is that the plant will establish more quickly. It is also expected that the plants will develop leaves and stems much faster than traditional methods.
However, there is one thing you must do to get the benefits of air pruning - raise the propagation/transplanting cells off the ground so that air can circulate around the bottom to kill the emerging root tips.
All plants require a range of different minerals for healthy growth. Usually, a plant absorbs the minerals it needs from the soil in which it is growing. However, with hydroponics you need to provide your plants with the minerals they require in the form of a nutrient solution. This allows you tight control over the minerals your plants receive.
Nutrients explained Nutrients contain essential elements that are vital for plant growth. If these essential elements, as well as carbon dioxide (CO²) and light, are made available to a plant, they can produce the compounds (food) the plant needs for normal growth. The most important elements are known as the ‘macro elements’. These consist of:
Nitrogen (N) - A plant uses Nitrogen for rapid growth and the development of foliage, leaves, flowers/fruit and seeds. Phosphorus (P) - Phosphorus plays a major role in transporting glucose (plant food), stimulating root development, and promoting flower/fruit and seed production. Potassium (K) - Like Phosphorus, Potassium promotes flower/fruit and seed production. It also helps to protect a plant from disease. All plants require large quantities of the macro elements. During the vegetative cycle your plants will benefit from extra nitrogen, while more phosphorus and potassium is beneficial in the flowering stage. Different nutrients are used to ensure that your plants receive all the minerals they need in the right proportions at the correct stage of their lifecycle. There are two types of nutrient solutions available:
‘Grow’ mix: A ‘Grow’ mix contains high levels of nitrogen; you should, therefore, use this nutrient solution during your plant’s vegetative cycle.
‘Bloom’ mix: A ‘bloom’ mix contains high levels of potassium and phosphorus, so change to this solution when your plants start flowering.
Plants also require other elements known as ‘secondary macro elements’ and ‘micro elements’.
Secondary macro elements are magnesium, calcium and sulphur. Micro elements (also known as ‘micronutrients’) are manganese, boron, copper, zinc and molybdenum. The table at the end of this document highlights why a plant needs each of these minerals.
Nutrient Solutions Nutrient solutions are available in one, two and three-part packs. They are normally in concentrate form:
One-part nutrient solutions
One-part nutrient solutions are very easy to use and popular with beginners or growers who prefer the simpler method of feeding. The one-part removes the chance of incorrectly measuring the components of the two-part and three-part.
Two-part nutrient solutions
Two-part nutrient solutions consist of two bottles which are added (in equal amounts) to water in order to supply a full spectrum of elements to your plants. As the nutrients are more concentrated and specific, you can achieve very accurate feed levels for your plants at all stages of their life cycle. This helps to improve plant growth and health. Two-part feeds are the most popular nutrients as they are easy to use whilst delivering good nutrient levels.
Three-part nutrient solutions
Three-part nutrient solutions require three bottles to complete the nutrient formulation and are generally more suited to the professional grower. A three-part solution enables you to provide your plants with the most precise nutrient management throughout their life cycle– even more so than a two-part. It allows maximum control over the nutrient delivered to your plants. Due to its more complex nature, three-parts are not suitable for beginners.
Maintaining the nutrient solution Maintaining the nutrient solution involves keeping adequate nutrient strength, pH levels and optimum temperatures.
The strength of nutrient is the amount of dissolved salts that a nutrient contains. Nutrient strength plays an important role in maintaining the health of a plant. If the nutrient is too strong, the leaves of the plant can become leathery, curl downwards or even burn at the tips. If the nutrient strength is too low, then the plant will turn yellow, stretch and become susceptible to disease. The strength of a nutrient solution is known as the ‘conductivity factor’ (CF) or ‘electrical conductivity’ (EC). These can be measured with a CF/EC meter, which allows you to maintain the required level for the stage of your plants life cycle.
The pH is the measure of the acidity or alkalinity of a nutrient solution. A pH value of 0 to 6.9 indicates the nutrient solution is acidic, 7.1 to 14.0 alkaline. While a reading of 7 shows the nutrient solution is neutral. Ideally, the pH level should range between 5.5 and 6.5. If you allow the pH level to fall outside of this scope, it will affect your plant’s ability to absorb nutrients. This results in poor yields and slow growth rates.
A good temperature around the roots can encourage root growth and nutrient uptake. Never let the temperature of your nutrient solution drop below 15°C, as cold water will limit the ability of roots to absorb water and minerals, and drastically reduce yields. Similarly, a temperature too high – above 30°C – will starve your plants of the oxygen they need for healthy growth. Ideally, you should aim for a temperature of approximately 21°C.
Additives Additives are extra supplements that can be added to nutrient solutions to help the plant use nutrients more effectively.
This can promote growth and improve the general health of your plants. Additives can also encourage specific processes, such as rooting and flowering. Although they’re not essential, additives can be very beneficial in achieving the most from your plants.
Maintaining all of the factors discussed in this article should help your plants to grow strong and healthy. If you require any more information, please don’t hesitate to contact us.
Please see below for a list of essential elements a plant requires:
Symbol Type Symptoms of deficiency Nitrogen N Macronutrient Stunted growth and/or yellow leaves. Purpling along the veins on the underside of larger leaves. Phosphorus P Macronutrient Growth stunted, very dark green plant, leaves develop grey to purple dead patches. Potassium
K Macronutrient Slow growth and /or yellow to brown margins on older leaves Magnesium
Mg Secondary Older leaves yellow; as the deficiency progresses, small brown patches develop in the yellow areas. Calcium
Ca Secondary Yellow/brown spots appear on the edge of leaves. These spots can also be surrounded by a sharp brown outlined edge. This often affects the older leaves first. Sulphur
S Secondary Small growth, all leaves turn yellow, reddening of the veins on the underside of leaves. Iron
Fe Micronutrient Uniform yellowing of young leaves, while the veins remain green. Eventually, the whole leaf becomes bleached. Manganese
Mn Micronutrient Yellowing between veins on young leaves, with brown patches forming along the veins. Boron
Younger leaves show a light yellowing/browning. A cluster of leaves develop in the same place. Leaf margins twist and leaves become brittle.
Cu Micronutrient Young leaves drooping, a wilted appearance, yellow to brown patches. Mature leaves may become bleached between the veins. Zinc
Zn Micronutrient Older leaves develop brown patches in between the veins. Young leaves very small and/develop in a cluster in the same space. Molybdenum
Mo Micronutrient Upward cupping of the leaves with mottling. Looks like nitrogen deficiency without the reddening on underside of the leaves.
Light is one of the most important factors in your grow room, and with current energy prices they are becoming more costly to run. With this in mind do you think you’re getting the most out of your light? One very important component to your grow light is the reflector. Every grow room is slightly different and in order to make it as productive as possible we stock a large range of reflectors to suit all growers’ needs.
Out of all the reflectors we stock at Aquaculture all are highly reflective with a dimpled aluminium finish. These can be organised into 3 categories:
Open Closed Air-Cooled Open Reflectors Excellent heat dispersal. These reflectors are used by the majority of growers; mainly because they are extremely versatile and are easy to use.
The ‘Euro’ and ‘Mantis’ reflectors fall into this category. ‘Open’ refers to the two sided design allowing the reflector to be open at either end. This type of reflector allows the heat that the lamps create to easily escape, which means they can be positioned closer to plants than closed reflectors. The ‘Mantis’ reflector (pictured above) is particularly good as it can be adjusted to allow for a wide or narrow spread of light to suit most grow room requirements. As well as allowing good heat dispersal; they inevitably let light escape from either end, making them suitable if you are using multiple lights in series. In single lamp applications this escaped light can be captured and used more effectively with closed reflectors.
Closed Reflectors Optimised light distribution. This type of reflector has four or more sides to it which causes the light to be focused downwards, allowing for a more concentrated and uniform spread of light over a given area.
The ‘Ultralite’ (pictured right), ‘Superwing’ and ‘Diamond’ are all considered closed reflectors. These reflectors are often used to optimise light output in single light grow rooms. They also come into their own when you want to maximise the efficiency of multiple lights to avoid cross over areas and lighting dead spots which can occur with open reflectors. With this design heat can build up within the reflector so higher mounting heights are necessary.
Air Cooled Reflectors Reduces heat output. The ‘Aerowing’, ‘Blockbuster’ and the ‘Cool Shade’ (pictured right) are all classed as air cooled, their enclosed design allows air to be pushed past the lamp and ducted out of your grow room; massively reducing the grow room temperature.
As the light has to pass through heat resistant glass a small reduction in light intensity occurs (around 3-5%). However, much less heat is given off by air cooled lights, so the environmental temperatures are often more favourable.
You can hang these lights much closer to the plants which makes a very efficient grow room. Air cooled reflectors are excellent in summer months, or in small rooms where hanging height may be an issue. To use an air cooled light you need a minimum of 200 m3 of air to pass through the reflector every hour. This can be achieved by installing a separate ventilation system for your lights or by using your exhausted air from your grow room.
When growing indoors, the power and quality of your grow light is arguably the most important aspect of your grow room. Without a doubt, your grow light can really make or break your final yield. So how do you make sure that your grow light gives you the best possible results crop after crop? Read on for some top tips on keeping your grow light shining bright!
How bright is your bulb? Simple fact; the light output from your grow light lamps will drop in intensity during the course of their working life. Whether you are using high pressure sodium lamps to produce flowers, or metal halide lamps to grow mother plants, it is a must that you replace your lamps on a regular basis.
So how often should you change your lamps? After 6 months? 12 months? Or every crop cycle? Ultimately, it comes down to how long they have been in use. However, not all growers use their lamps for the same time each crop cycle.
High Pressure Sodium (HPS) Lamps HPS lamps efficiently produce mostly red/orange light, which make them suitable for flowering and fruiting plants. However, their efficiency in turning electricity into plant usable light also makes them suitable for vegetative growth.
When deciding to replace HPS lamps, we should always consider the amount of time they have been used, as opposed to the amount of crop cycles. Why? Well, quite simply, one grower may use their lamps very differently to another. Take the following example:
Grower A - This grower may choose to grow 4 big plants in a 2m x 2m x2m grow tent with four 400W HPS grow lights. He uses an 18-hour photoperiod when veg’ing his plants for 6 weeks, and then flowers them under a 12-hour light cycle for 10 weeks. So every complete crop cycle he will use his lamps for 1,596 hours.
Grower B - Using a grow tent of the same size, this grower may choose to grow 12 smaller plants with the same 400W lights. He uses an 18-hour vegetative cycle for 2 weeks and then flowers for 8 weeks. So every crop cycle he will use his lamps for 925 hours.
Looking at the published data (see graph at the bottom) for the most popular horticultural HPS lamp - the Sylvania Grolux 600W Dual Spectrum Lamp - we can see that for the first 6,000 hours of use, the lumen maintenance (total light output) drops by 1% for every 1,000 hours of lamp-use. If all other growing factors remain steady between crop cycles (environment, nutrients, growing system, plant type, etc), the amount of light is directly proportional to crop yield. The example above shows that two different growers have very different crop cycles - each using their grow lights quite differently. So in order to know when your lamp needs replacing, you need to know how many hours it has been used for. After 12 months of back-to-back growing, Grower A will have completed 3 crops, whereas Grower B will have completed 5 crops. Both growers will have used their lamps for a similar amount of time, and both would have had a 3-4% light output reduction - which can equate to the 3-4% yield reduction.
So how often should you change your HPS lamps?
At Aquaculture we recommend using your lamps for a maximum of 4000-5000 hours – approximately 9-12 months of continuous back-to-back growing. If you want to look at it more closely, the answer ultimately comes down to the value of your crop. If your lamp replacements are going to cost you £100 after 6 months of use, and a 2% yield reduction is going to cost you £200 – it makes financial sense to replace your lamps.
Metal Halide (MH) Lamps MH lamps are quite different to HPS. The blue light they produce makes them more suitable for vegetative growth or for supplementing multiple HPS lamps with extra blue light.
Over time, the light output of MH lamps decrease much faster than HPS lamps. Where a HPS will drop 2% after 2,000 hours of use, a MH lamp will drop 9%! As you can see from the graph (see below), the reduction at 4,000 hours is 15% for MH and 4% for HPS.
So how often should you change your MH lamps?
If you are using MH lighting specifically for vegetative growth and swapping for HPS lamps at the start of flower, you should change them every 2,000-3,000 hours of use (12-18 months of back-to-back growing, or 5-6 months of continuous 18-hour vegetative growth).
This graph shows the lumen maintenance factor for both Sylvania HPS and MH lamps over 8,000 hours. The BLUE line is MH, and the RED line HPS. All data taken from www. sylvania-lamps.com (09/2011)
Reflectors are very important for HID lighting systems that are powered by HPS or MH lamps. They help reflect light emitted from the top and sides of lamps, and a good reflector should reflect 50% more light than using a lamp without a reflector.
Reflectors are made from various types of hammered aluminium.The better ones are made from miro aluminium - which is around 96% reflective. Over time, and through heat exposure from the lamp, this reflective surface slowly oxidises; resulting in a significant drop in reflectivity. Data from the Dutch lighting manufacturer, GAVITA Holland, shows that even high quality miro aluminium will lose approximately 1% of reflectivity for every 1,000 hours the light is on – this is in a clean greenhouse environment! Unfortunately for us, indoor growing environments are often much dirtier and dustier than greenhouses. Our reflectors are very close to our plants and will, over time, get dust, dirt and even stray foliar sprays deposited on the reflective surface. This problem is then increased tremendously for growers using humidifiers or sulphur vaporisers. If using a humidifier with tap water, you will see a white dusty deposit form on most grow room equipment (and even the plants leaves). This white dust is the bicarbonates from the tap water, and unfortunately makes reflectors not very reflective.
You can expect your reflector to lose around 5% of its original reflectivity over the course of 12 months in a clean grow room. This can increase to 10% in a grow room using humidification or a sulphur vaporiser. That 10% loss in reflectivity means 5% less light that your plants could be using.
So what can you do?
To maintain high reflectivity from your lighting system, it is essential to clean your reflectors regularly, and consider replacing them every 12-18 months for maximum light output. For advice on choosing the best reflector for your set up, feel free to visit us in store to speak to one of our friendly members of staff. Or alternatively, you can call 0845 644 5544 for any queries.to use a RO machine to filter the water when using a humidifier. This will generate pure water and remove the bicarbonates that decrease the reflectivity of your reflector.
When using a sulphur vaporiser, never have them burning when the lights are on. Cleaning your reflector with a soft microfiber cloth and a mild acidic solution will remove some of the dust, dirt and bicarbonates from humidifiers. But remember, cleaning a reflector will never return it back to its original state, unfortunately. The decrease in reflectivity is taken very seriously by commercial growers in the greenhouse sector that use artificial lights. Despite being on a budget, these greenhouse growers consider it very worthwhile to replace reflectors every 12 months! The picture (below) shows hundreds of GAVITA Hortistar reflectors recently removed from a greenhouse in Holland (taken March 2011).
Very popular with growers of all abilities, coco coir (also known as just coir) can help you to achieve great results with your plants in terms of growth, yield and quality. Here we explain what coir is and the benefits it gives you – and your plants! We also detail how you can achieve great results when growing in coir.
What is Coir? Coir (pronounced ‘koy-r’) is the term give to a range of natural products made from coconut husks. From the coconut husk there are main horticultural coir products that can be extracted - these are coir chips, coir fibre and coir pith (also known as coir dust).
Coir pith is the main constituent of most coir products available. It is very good at holding water while still providing adequate air space. This is due to the millions of micro-sponges that make up the pith; allowing it to hold up to nine times its own weight in water. Coir pith also has a unique cation exchange capacity which, when treated correctly, makes it perfect for hydroponics.
Coir chips and coir fibre are coarse coir products, and are often mixed with coir pith to lower the water-holding capacity and improve air-space and drainage. Coir chips can be purchased on their own for making custom mixes with coir pith, or can be used on their own in flood and drain hydroponic systems.
Benefits of Coir As coir is derived from coconut husk, it is completely biodegradable. This makes coir an environmentally friendly hydroponic growing media. Roots establish very well in coir due to the air-space and water-holding properties, but also because of the presence of naturally occurring Trichoderma - a beneficial fungus. It can be used in a variety of systems including the AutoPot, Flood and Drain (when mixed with clay pebbles), hand-watered Pot Culture and Drip Irrigation Systems. Coir is very easy to work with, and is suitable for beginners and professionals. Aquaculture sell a few different bagged coir products: Canna Coco Professional Plus, Gold Label 60/40, VitaLink Coir Mix and VitaLink Coir Chips.
Canna Coco Professional Plus contains mostly fine coir pith with a small quantity of coir fibres. This creates a coir growing media that holds a lot of water, making it suitable for hand-watering and drip irrigation. When using it in flood and drain systems, it needs to be mixed with coir chips or clay pebbles. Some growers like to mix 5-30% perlite with Canna Coco Professional Plus to help with structure and aeration.
Gold Label 60/40 contains 60% clay pebbles and 40% coir pith. This mix is used mainly for flood and drain systems, but can also be used for drip irrigation or where lower water content is required.
VitaLink Coir Mix contains a mix of 70% coir pith and 30% chips and fibres. This makes a coarse coir mix that holds less water and drains more freely; making it more suitable for frequently irrigated hydroponic systems such as drip irrigation and Autopots. VitaLink Coir Mix is also great for propagating young plants, and can also be used in flood and drain systems when mixed with more coir chips.
VitaLink Coir Chips are coarse and do not hold as much water as coir pith. These are used for mixing into other coir products to lower the water-holding capacity for frequently irrigated systems such as flood and drain. Coir chips are also used as a mulch on the top of pots and also as a layer on the bottom of the pot to aid with drainage.
Growing with Coir What is Buffered Coir?
Before being washed and/or buffered, coir pith contains a lot of sodium ions. These are held tightly by the coir’s unique cation exchange properties. Coir pith also contains high levels of potassium which is released slowly throughout its use. In order to make coir suitable for use as a hydroponic growing media, it is first washed with water to release some of the free sodium, and then it is soaked with a solution containing high levels of calcium. The calcium displaces the sodium from the coir, and after this soaking period the coir is again washed to remove the displaced sodium, leaving the calcium in its place. This whole process is known as buffering, and prevents the coir from holding onto calcium and magnesium, which are important nutrients for plat growth, and eliminates sodium toxicity issues.
Coir Specific Nutrients
As explained in the buffering process, coir preferentially holds onto calcium and magnesium, and also slowly releases its naturally occurring potassium. For this reason you should always use a coir specific nutrient like Canna Coco or VitaLink Coir which have elevated levels of calcium and lower levels of potassium. This will allow you to achieve optimum results from your plants. If you are mixing coir with other media, like clay pebbles, you can use hydroponic nutrients if the clay pebble content exceeds 65%.
Before using Coir
Coir does not contain a full range of nutrients for plant growth, so before planting, coir should be irrigated with a nutrient solution at a strength suitable for your plants until runoff occurs.
Checking the nutrient levels within your coir Coir holds onto nutrients more so than other hydroponic growing media and just checking the run-off does not always give an accurate picture of the nutrient strength in the coir. The procedure below is known as a 1:1.5 extraction, and can be used to give a more accurate representation of what is occurring in the coir:
Take a 250ml measuring jug and fill it with 150ml of de-ionised or reverse osmosis water. Remove small samples of coir from as many places as possible in the slab/pots. Add the coir to the water until it reaches the 250ml mark. Mix and allow it to settle for at least two hours. Filter and measure the EC/CF. *Simon’s tip – Regularly checking the EC/CF of your coir helps to build a sound irrigation strategy.
Moisture of Coir
To achieve a higher level of air within your coir it should not be kept constantly moist. A good way to determine whether your coir contains the appropriate level of moisture is to lift your pots/slabs and determine the weight. If your pots/slabs are very heavy, they will be full of water. However, if they are very light, there will be very little or no water.
Irrigating Coir Drip systems:
Fewer, larger irrigations work best with coir. Drainage is improved and water and nutrient is best utilised if the frequency of irrigations is low and the amount of the solution is enough to get between 20 and 40% runoff. Typically, fully grown plants should need irrigating between 1 and 3 times a day depending on plant size. VitaLink Coir Mix does not hold as much water as 100% coco pith, so irrigations for fully grown plants should be 3 to 6 times a day.
Flood and drain:
When using coir in flood and drain systems it is recommended that you mix it with clay pebbles or coir chips. Ready to use or homemade mixes of 40% coir and 60% pebbles are ok (ideally, 25% coir with 75% pebbles (or coir chips) is better). During a flood cycle the growing media becomes fully immersed in nutrient solution; making it fully saturated. And then after the drain cycle it can take quite a long time before it needs irrigating again. For this reason you should only need to flood a maximum of twice a day with 60:40 mixes and four times a day with 75:25 mixes for fully grown plants.
Hand watered in pots:
Watering from the top of the pot is recommended, and you should water as and when the pots feel like they need it (do not water if the pots are heavy). As they reach one third to half of their original weight, it is time to water. As a guide, young plants in large pots should need watering every 2-3 days and fully grown plants should need watering once a day.
After planting into the AutoPot you should hand water from the top of the pot for the first 14-21 days. When doing this you should allow 10-20% of the solution you pour into the top to run out the bottom of the pot, this runoff should be discarded. This gets the roots established throughout the pot before you start constantly watering from the bottom. The AutoPot system delivers a continuous supply of nutrient solution to the pot. This can sometimes cause the growing media to become overly wet, particularly if the plants are small.
It is recommended that you mix 20-30% perlite or coir chips into fine coir when growing in AutoPots to help aerate the growing media and prevent over-saturation. Alternatively, use a pre-mixed coarse coir like VitaLink Coir Mix.
Reusing Coir Coir products are often discarded after use, but this is very wasteful as coir can be reused up to 4 times! Good quality coir will keep its structure and its nutrient retention properties because it is very slow to decompose.
So how do you re-use coir?
After harvesting your plants, remove the coir form the pot or slab packaging and break apart with your hands or a hand trowel. Remove the crown of the stem and as many of the large roots as you can (do not worry about removing all the roots; they will break down over time during your next cycle and will not cause problems with disease).
Once you are happy that with the amount of remaining roots, put the coir back into the pot and wash through with water that is roughly half the volume of the pot – so if you have a 10L pot, pour through 5L of water. Allow the coir to fully drain. After this pour through a nutrient solution at a suitable strength - roughly a quarter the volume of the pot. This process will remove the old nutrients from the previous crops, and replace with fresh nutrients ready for planting.
Simon’s Tip – When reusing coir, it is good to use beneficial microbes and enzymes through the plants life cycle to help break down dead roots and keep the coir and plants’ roots healthy and productive.