What is happening to my cucumbers?
I bought bush cucumber plants a month ago that my provider assured me would do fine in pots. They had a growth spurt, set blossoms but now the leaves are turning yellow. Not enough sun? Too much sun? Too much water? I'm afraid I'm going to lose them if I don't do something quickly.
Yellowing leaves are often a sign of nitrogen deficiency. Plants in pots are particularly susceptible, because whatever nutrients/fertilizer was there gets washed away when you water, and there's no way for it to replenish itself.
Try giving the plants a weak mixture of a liquid fertilizer once a week or so.
Last year we had a lot of rain. This happened to my cukes growing in pots. On a garden tour I noticed same situation at someone else's garden but the nearby cukes growing in the soil looked fine. I think mudster is right, esp if you've been having a lot of rain. I think the nutrients just wash out of the soil in pots. I would agree with his recommendation to provide weekly liquid fertilizer.
I grew a climbing cucumber vine in a big pot last summer, and had a similar problem; my flowers didn't set fruit, and the bottom leaves started turning yellow. Mine were in a pot under my eaves, so they got about 4-5 hours direct sun in the late afternoon.
The bottom leaves seemed to die off over time regardless of what I did, so if it's just the bottom leaves, don't worry too much. If it's leaves all over, then it might be what mudster suggests, a deficiency in the soil in the pot.
To get the flowers to set fruit, I increased my watering slightly (I'd been very disciplined, feeding it 2 litres once a day or every two days; I increased this to every morning). Basically, enough so that the plant didn't wilt terribly by the end of the day (a little floppiness is alright, but looking like it's in pain is not!). And I fertilised the flowers myself, using an earbud to transfer pollen from the male flowers (no little cucumber behind the flower) to female flowers (little cucumber behind the flower head). This worked well.
It is essential that you never touch the leaves when they are wet. Don't know if that is your problem, but something to keep in mind.
Yellowing leaves can also be a sign of overwatering. Stick your finger in the soil, and if it's pretty wet, back off on the water a bit.