In this article, we look at a few of the most common causes of leaf damage including nutrient deficiencies, overfeeding, underfeeding, over-transpiration and wind burn. Includes a Plant Recovery Plan to get your plants back on track.
Leaf Damage
The leaves and new shoots on your plants are the often the best indicators of how healthy your plant is and are usually the first things to show visible signs of any problem with under feeding, overfeeding or the environment. Many things cause leaf damage and it’s not always easy to accurately identify the problem, therefore whenever you encounter any problem in the garden the first thing to do is take immediate action. The procedure below will remedy most problems and hopefully the plants will already be on the road to recovery by the time you discover what the cause was.
Emergency Procedures – Plant Recovery Program in Hydroponic Systems
Check leaves for tiny bugs – This is the first thing to eliminate as a potential cause of your plant health problem. If you find bugs that can harm your plant then take the appropriate action to remove them immediately. Please call our technical team if you are unsure about what action to take on 0845 345 5176.
Move lights a further 30cm (1’) away from your plants – This will relieve damage from over-transpiration and heat stress. It will reduce the demands on the plant and speed up the recovery process, whatever the problem may be.
Check root zone – The roots may be discoloured, this is not unusual or a problem in itself, but if they look mushy or pull apart easily your nutrient solution may be too warm(no oxygen) when the light is on, and/or a root disease or pathogen like Pythium.
Turn solution pumps off – In preparation to Drain the nutrient solution. Flush through cubes, pots, or slabs with an appropriate strength feed – This will leave approximately the right strength feed in the pot or cube. Make the solution slightly weaker than normal if anything. This will cure any overfeeding without going to the extreme of using water. Add SuperThrive and Oxy-Plus if possible.
Pump out all of the old nutrient solution including the flush – In preparation for the new solution.
Add a fresh nutrient solution to the system – Check for signs of overfeeding or underfeeding and change the strength of your new nutrient solution accordingly. This should cure under or overfeeding problems. When dealing with overfeeding problems, you may wish to add some Clearing Solution which will help the plant flush excess nutrient and return to a healthy state.
Check position of oscillating fans – Air movement is good for your plants, but fans can sometimes cause wind burn and leaf damage if air is blown onto the “light facing” tops of leaves. Reposition your fans to blow directly at the lamp or blow up through the plants.
Check your ‘lights off’ temperature/humidity in cold weather – Cold nights can cause lightening in the colour of leaves as well as leaf tip and margin damage. This can result in low yields. Your ‘lights off’ temperature should be maintained at 10oC below your ‘lights on’ temperature for best results. This will usually be around the 18-20oC level.
Check your ‘lights on’ humidity – The leaves may struggle if the humidity is too low. Increase the size of air intake holes into the grow room, and try not to bring too cold air into the grow room.
Now try to further investigate the source of your plant’s poor health so that you can try to avoid similar problems in the future. Be patient if you think you may have cured the problem using the above recovery procedure as the plant may take a few days to show signs of improvement, especially if it has been overfed. Keep an eye on new shoot growth as hopefully before long you should be getting some on a daily basis and this is your best indicator that things are on the mend.
Nutrient Deficiencies
All good hydroponic feeds are designed to be complete nutrient packages and nutrient deficiencies are fairly rare when using one of these nutrient regimes. This is especially true for micro-nutrient deficiencies such as calcium and magnesium unless you have very soft water and have been underfeeding your plants. In hydroponics, if you do get a micro deficiency it is more likely to be caused by a nutrient “lock out”. This can be caused by overfeeding or excessive adjustment of pH with phosphoric acid in hard water. Nutrient lockout of this kind can also occur if you are using the wrong feed. Either way these sort of deficiencies are not common and the main indicators of a micro deficiency such as rust spots, lightening between leaf veins, and leaf damage are nearly always environmentally caused rather than deficiency based. Micro-nutrient deficiencies like iron, calcium and magnesium will all show first on new shoots and new leaves as they are non-mobile elements.
Non-mobile elements are those which the plant has no control over the distribution of throughout its structure and thus any deficiency will always show first on new growth. If deficiencies and damage appear on lower bigger leaves and not on the newer leaves then this would not be a micro-deficiency and would either be natural leaf loss with big fast growing plants, a slight main element (NPK) deficiency or again a slight environmental problem.
Main element deficiencies such as insufficient nitrogen will always show on the bigger lower leaves first as they are mobile elements and can move to where they are needed in the plant (at the top where the light is). Obviously, the plant will move these main elements to the place in which the most activity is taking place, and any deficiency will show in the more established leaves at the base of the plant where relatively little is happening. If your plants start to lighten in colour generally, and you are losing a few big leaves you may need to increase feed strength slightly.
You must also remember that it is normal for a plant to shed its big lower leaves after a while so that younger leaves nearer the light can take over and replace them.
Try to keep the plant a nice green colour, not too light or “limey” (underfed) and also not too dark green (a bit too well fed).
Remedy: Follow Plant Recovery Program.
Over-feeding symptoms
The main symptoms will be downwards hooking on the leaf tips and sometimes leaf margins. This is a dead give away and a certain sign that overfeeding is the cause of your plant health problem. In the early stages the plant will usually go a dark dull green with some tip burn. The leaves curl down in an attempt to retain moisture as the high nutrient strength sucks the water from inside the plant out through reverse osmosis. It does this in an attempt to balance the pressure across the root membrane.
Remedy: Follow Plant Recovery Program.
Under-feeding symptoms
The whole plant will be lightening in colour and the problem will be worse on the lower parts of the plant. There will be no associated leaf curl. If the lightening is only at the top of the plant it may be due to bleaching from the light intensity.
Remedy: Follow Plant Recovery Program.
Over-transpiration Leaf Damage
You may not notice the early symptoms of this problem, as the leaf loses its thick healthy smoothness and appears a little mottled in colour, maybe slightly lighter between the leaf veins. This occurs because the leaf has sweated too much in the heat and light. The leaf tips and margins may also curl up sometimes as the leaf tries to retain moisture. It only really shows as damage a couple of weeks later as rusty spots appear between veins, leaf colour loss generally leading to dying off of that leaf. Over-transpiration is more of a problem for younger plants in vegetative/18 hour light cycle and the main reason many large multi-light gardens use CO2 in the 18 hour cycle, to help with the heat and prevent leaf damage.
Remedy: Follow Plant Recovery Program.
Wind Burn Leaf Damage
This is a common grow room ailment and is caused by blowing oscillating fans too heavily on the tops of leaves where there is a lot of light and heat. The fans can suck all the moisture out of the leaf causing the leaf tips and margins to curl up, die back from the tip, go a golden colour and become crispy.
Remedy: Follow Plant Recovery Program.
If you experience any symptoms that are not covered here, then please do not hesitate to call our technical team on 0845 345 5176 and we can advise you on the nature of your problem and the best course of action.
