Cucumber plant problems

[Kat]

Hello!

I am growing mini cucumbers (cornichon) indoors under a grow light, alongside a few other plants that are doing well. The cucumber plant has been struggling though. The leaves have been turning yellow and dying for a while, and the growth seems to be stunted. I read that it might be a potassium deficiency if the old leaves are dying and the new ones are kind of cupped/puckered. This seems to match what’s happening to my plant. Pictures attached. I’ve started feeding with a balanced fertiliser which seemed to help at first, but now the plant seems to be struggling again. Any tips would be much appreciated!

 

[headfullofbees]

Looks very much like you have a nitrogen deficiency too.
If you have access to herbivore (cattle/horse/sheep) or chicken manure, steep it in water for two hours, before using a little on your growing bed, leave the manure in to strengthen the brew, then use at every other watering.

 

[Kat]

Thank you! All I have access to is organic liquid feed. I have several kinds, and have already been feeding weekly with a 3-5-4 feed at about 2-3ml per litre. I could increase the concentration?!
It’s strange because other types of plant right next to this one have been treated the same and are large and thriving!

 

[headfullofbees]

Do not increase concentration, use at the concentration stated.
My fear is root rot.
Water as little as possible, & water & feed at approx 3" away from the stem.
Put a layer of DRY compost in a 2" dia ring around the stem to encourage new root growth approx 1/2" deep to encourage new root growth, but don't water that compost at all, it will get damp enough for your new roots by capillary action.

 

[Kat]

Ah, thank you very much for this! I will try it.
Much appreciated!

 

[jbclem]

If you have a magnifier, or handheld microscope, you should check the underside of the leaves and see if you have something like thrips. You need 10x to 15x magnification. I use a device like this:

https://www.amazon.com/Carson-MicroMini-Lighted-Microscope-Flashlight/dp/B015MS3ICQ/ref=sr_1_13?dchild=1&keywords=led+handheld+pocket+microscope&qid=1608191525&sr=8-13

or this:

https://www.amazon.com/Magnifying-Stretching-High-Power-Ultra-Clear-Microscope/dp/B07QNWTDQ6/ref=sr_1_21?dchild=1&keywords=led+handheld+pocket+microscope&qid=1608084041&sr=8-21

I use them mostly for spider mites, but recently discovered thrips and damage a bit like I see in your photos. These devices are cheap and work really well for pests you can't see with your naked eye.

 

[peherar199]

hi

 

[headfullofbees]

Hello. Welcome