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Solving Some Common Summer Problems |
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| For all those people who are trying to grow indoors under lights, and especially for all those first time summer growers, here are all the important things you need to know to get a successful harvest this summer. |
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The main physical factor we have to work around during summer growing is the warm ambient outside air temperature. During the summer months, the grow room is probably warm enough before we even turn our lights on. The excess heat is generally not problem if the grow room is set up correctly, with sufficient air being drawn from inside a lived in house, and hot air extracted not only from the grow room but also the entire building. This is an ideal scenario where the air drawn in is high in CO2 at a friendly temperature and with few bug problems. This scenario works well all year round and eliminates the many environmental problems associated with using outside fresh air in winter and summer.
The ideal growing temperatures for most light loving plants are 21-24C lights off, and 24-27C lights on. Temperatures will always be high in the lights on cycle - be more concerned with how the plant looks on a daily basis that worrying about temperatures. Does the plant look healthy? Is it growing at the new shoots every day? Is it a nice colour? Is there any leaf curl?
NOTE: Always measure “Actual Temperature” (measured in the shade) as any radiation from the lamp will give you falsely high readings.
Problems in the propagator
The main causes of failed rooting of cuttings are too much heat and/or too much moisture.
You may also see some yellowing of the bottom leaves in summer. You shouldn’t worry about this as it usually indicates the cuttings are starting to produce root nodes and are using the transportable mobile nutrient elements in the leaf for food. (tip: once rooted use Green Up to restore the plant’s colour)
Spider Mites
While the new cuttings are in the propagator, this is a good time to start checking for bugs especially spider mites. Spider Mites can be tackled effectively at this stage by introducing live predators into the propagator or by manually removing bugs and submerging the top side of the plant in a solution of buzz off once rooted properly. A regular 5 day bug check in all your grow rooms is recommended, especially as they will breed much quicker in warmer conditions. For more information about grow room pest control see our article on dealing with Spider Mites Here.
The more common problems:
1. Heat
Problems with too much heat can seriously affect rooting rates in cuttings. To avoid the propagator getting too warm move your light slightly further away than it was in the winter. A good idea is to adjust the lamp height to help control the temperature inside the propagator, always keep the light at a reasonable distance though!
If your using a heated propagator make sure it’s not too warm, you could use a timer on the propagator to cool it a little and make sure the propagator and media (cubes) are not too wet if using bottom heat or damping off or rot problems may occur before rooting is completed.
If possible have some gentle air exchange on the rooting area to avoid heat build up or make sure it’s not too enclosed.
Ideal propagator temperature – 21 to 26 C. (70 to 80F)
Slight differences in ideal temperatures with this range are due to differences in latitudinal origin between different strains and varieties. Any temperature within the above range should work well. Some species and varieties may need fine tuning.
2. Moisture
Excess moisture is often a major cause of failed rooting, especially when propagators are hot the cuttings may rot or just not root and die.
To avoid problems make sure:
- rooting cubes are not too wet.
- No water or solution in the propagator tray.
- Only a light mist of moisture should be visible on the propagator lid, if moisture droplets are rolling down the side of the lid, it’s too wet and the vents should be opened more.
- Don’t mist the plants every day. When you do mist wipe the excess moisture from the lid first.
Ideal humidity – 73% to 83% Relative Humidity (R.H.)
Problems in the vegetative growth (18 hour) room
Most plants do most of their growing in the first half of the day, and 18 hours under all that light and heat is a long time and I would expect perky leaves in the morning and a little droopier leaves towards the end of the cycle, this is quite normal although you must check there is no droop caused by warm nutrient temperatures and consequently less oxygen to the root zone. Protect tanks well from light and heat with extra layers of white reflective sheeting.
Younger plants don’t need as much light, and can’t deal with the associated heat so well as when they’re bigger and older. Don’t get too close with the light until they start to flower, in flowering they can control their body temperature better and don’t tend to over transpire like they do in their vegetative cycle. Until the plant gets into flowering, health and good colour are our main considerations. If we can keep the plant healthy and bug free to this point (The Point of no return!) then we are sure to get a result. This means moving your light away a few inches further than normal when the warmer weather is here.
Spider Mites
While the new plants are in their vegetative cycle they are at risk from spider mites which can be brought in on your clothes or just find their way in naturally. Spider Mite can be tackled effectively at this stage by introducing live predators into the grow room, a 500 predator vial is good for 5 plants. It’s best to remove the worst leaves fist and use a spray 5 or 6 days before introducing the predator mites. A regular 5 day bug check in all your grow rooms is recommended, especially as they will breed much quicker in warmer conditions.
Heat
When the ambient air temperature is high, like it is in the summer, we must try and keep heat down and health up at least until we get to our PNR (point of no return) at the beginning of flowering. Until then we have to do the best we can to get optimum growth while retaining plant health by not letting the plants get too warm and over-transpiring.
Our best tips:
- Use grow rooms with decent headroom and good air exchange/extraction.
- Have your light on cycle during the our night time when the ambient temperature is lower.
- If your growing in a tight area use open ended reflectors to avoid heat problems.
- Consider using an input fan, this will help cool the area and aid exchange rate.
- If not using an input fan then have more than one good size input air holes near the bottom.
- Use oscillating fans to help cool room, reduce any still air spots and strengthen the plants. (be careful not to wind burn the plants.)
- Consider a light rail, to spread the light and heat.
- Your only as good as your weakest link. The plants will have a lot easier time dealing with optimum light and the heat of the summer in a hydroponic system with all that air and water around.
- Check nutrient solution temperatures, especially towards the end of the day.
- Cover gro-tanks and nutrient solutions with an extra layer of white reflective sheeting, this will hopefully prevent the solution getting too warm.
- Good quality Jet Stream Air Cooled Lighting Systems from Canatronics are now available.
- Light spreader/heat shield are also useful especially with 1000 Watt systems
Over-transpiration
Over-transpiration damage on leaves is in most peoples’ indoor gardens especially in the summer. It’s caused by too much heat and in the leafs attempt to keep cool it over transpires moisture from it’s leaf, in the same way when we sweat and the process of evaporation of the moisture sweated causes cooling of the surrounding area. In the leafs case it may look a bit blotchy and lost it shiny, thick, smooth green look for a few days and then start to loose colour generally and especially between the leaf vains where rusty spots start to appear.
These later symptoms of colour loss, rusty spots and general leaf damage usually shows themselves after a couple of weeks a few inches under fresh growth, indicating it was a bit hot one or the light was a little close one day a couple of weeks ago. The bigger the plant gets the easier it can deal with the light and heat, always check new growth and move the light away slightly if your in doubt. This condition is often mistaken as a nutrient deficiency, which are actually quite rare and 90% of all leaf damage and rust spotting is environmental not nutritional.
Stretching
Stretching plants can be caused by several factors. The most common factors are:
- Plant variety (genetics)
- Temperatures around the plant, especially around the tops
- Amount of light around plants, especially around tops.
If the reason that your plants are stretching is down to their genetics, you can prune the top of the plant out which will encourage the plant to bush out slightly more. Maybe try some different genetic stock if stretching becomes an ongoing problem.
Wind Burn
This is a common problem in the summer when using oscillating fans in the grow room. You have to be careful not to blow to hard on the top surface of the leaf where there is a lot of light or you can draw too much moisture from the leaf. At first your leaves will start to curl up slightly at the tip and margins in an attempt to retain moisture. Then the leaf will start to die back a golden brown colour from the leaf tip, the dead part will soon become brittle and crispy. Aim you fans away slightly or more directly at the lamp.
Take a look at our article on dealing with Spider Mites Here.
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