Im growing hydroponic cucumbers for the first time and I'm having trouble diagnosing what's wrong. These are from seeds (Spacemaster 80) and they germinated approx first week of October. They started out very well but took like 3 weeks to start growing up. They created large dark leaves and I recently pruned them as all of the flowers were hidden down below and there was some dying leaves turning dry/brittle in places as I don't think they were getting any light. Ive had some leaves with yellow spots and as they grew taller I've seen that most of them including the new ones have yellowing around the edges. I'm using a base hydroponics nutrient solution from Hydroponics Research called Veg+Bloom (RO/Soft). I started growing in their Hard/Tap formulation but changed that out once I got an EC meter and found out my tap water was well below 200ppm. I also added 5ml of Cal/Mag per gallon. My EC is around 2.0 and my pH is about 6.3. I'm using a Chinese knock off light which is supposed to be a "600W" LED. It's hanging about 33" from the base of the plant and cannot go any higher. I have air movement but not direct air. The temp in my room is about 70-75F and not sure of my relative humidity. The leaves feel thin and rough and have a crisp to them I'm not sure if that's normal. Pictures of my setup and some problem leaves attached. Leaves are also cupping down (too much light?). Also something odd is a lot of the leaves have spots where holes are but not sure if that's from me handling them. I also sprayed a foliar cal/mag spray a few days ago but not sure that helped any. I have more pictures if needed. Thanks for the help!
New York County New York
Thank you for your question. This appears to be interveinal chlorosis, a deficiency of iron. But, as the following Extension article explains, it may also be a deficiency in either magnesium or manganese, depending on which growth the chlorosis appears. http://cea.cals.cornell.edu/resourcesPublications/otherResources/Fe%20Def%20Spr2016.pdf
I think this should you help diagnose the exact nutrient deficiency, and adjust the pH of the water accordingly. You might also wish to consider having a nutrient test done, should a pH change not cure the issue. I hope this is helpful. Good luck!
My first thought was Iron too but the symptoms haven't moved to new leaves only. Would the older leaves recover from their nutrient deficiency if it was mobile or would the damage be done? Also is it typical that cucumber leaves are crinkly and papery? It's almost like the leaves are drying out. is that part of any deficiency?
I’m uncertain about how to answer. Immobile nutrients (iron) remain in old growth, so deficiencies appear in new growth, and old leaves appear to be okay. Mobile nutrients move into new leaves, so old growth appears deficient. If your plant has iron deficiency, you must acidify the water medium closer to that range indicate in the article. Other leaf problems are likely to relate to this.
Leaves drying out is an indication that the plant tissue is dead or dying, a predictable consequence of chlorosis.