Recently have been experiencing slow growth in my plants and have been seeing specific signs of some kind of problem on the leaves. They are showing two signs in particular, not sure if they are related:
All leaves have pale yellow spots especially around the edges. The leaves are also generally yellow in colour but looking at them under light shows clear round spots. (images 1 and 2).
Older plant and leaves have transparent dots which are sometimes just round holes. They are mostly very small round dots. In some plants, they are larger with brown outlines (image 3)
I am currently growing them in coco coir and perlite with some organic pellets. I am currently not adjusting pH but have bought a testing solution for the future. I am using a chemical fertiliser by GROW!IT formulated for pepper growing in coco (NPK 2.4-0.9-1.4) which is supposed to contain all needed trace minerals. I feed them with every watering as coco is inert and at a low dose. I did also recently add some fish blood and bone to the surface ( I am now aware mineralisation is unlikely in coco).
I am thinking it could be due to overfertilisation of nitrogen as the chemical fertiliser only contains inorganic nitrogen along with some kind of other deficiency. I believe sun scald or a pest infestation is unlikely as they are growing on a semi-sunny windowsill and there are no obvious signs of insects.
Can anyone ID the problem? I’ve looked up symptons for deficiences but can’t seem to match it with anything. Any help is appreciated.
by euanus420
1 Comment
PH most likely since you have no idea what you are feeding them. Did you precharge the coco? If not could be holding on to your magnesium or calcium. Are you watering to runoff? Might try flushing them with some quarter strength solution in case it is salt build up. The dead spots are necrosis from nutritional issues and not caused by pests in my experience. I wouldn’t underestimate the effect PH has on hydro and nutrient uptake. For example Fe3+ is absorbed 1000x more by the plant at a PH of 5 then it is at 6.0. So easy to get Iron/Manganese toxicity with low PH. What are the percentages on the back of the fertilizer? I find it hard to believe it has no other macro or micro nutrients than just NPK. First thing is getting a PH meter though. The $13 ones on Amazon by a brand called Ruolan are really good and come precalibrated. You should also get an EC meter at some point so you can test your runoff. What you put into the coco PH and PPM wise should be what you are getting out. If not the coco is holding on to your nutrients or you have salts built up. Feeding at 6.2 for a bit should help turn things around after you flush. You are probably low on light also though if it is just running in a window. Also going to need some PH up or down from a hydro store so you can adjust your nutes.