Cucumbers producing flowers but no fruit
I have a problem with my cucumber plants. They have been growing well and look very healthy. I have seen lots of flowers so far but no cucumbers. I grew them last year with no problem and I'm not sure where I am going wrong. Should I fertilize them?
It is normal for cucurbits to produce only male flowers at first. Female flowers will have a swelling below the petals which contains the ovaries that develop into cucumbers. Check your flowers to see if they are male; this would explain the absence of fruit. Watch for female flowers to develop within a week to 10 days of the first male flowers. It is thought that the benefit of this to the plant is that by the time female flowers do appear, the male flowers have already started to attract pollinators.
As far as fertilization goes, avoid overfertilizing with nitrogen as this will promote vine/vegetative growth more than flower and fruit production. From a Purdue University fact sheet: Add a complete fertilizer such as 4-8-5 or 6-10-10 or similar analysis at a rate of 1 to 2 tablespoons per hill prior to planting. Nitrogen is readily leached from light, sandy soils. Ensure an adequate nitrogen supply by side-dressing with ammonium nitrate (33-0-0) or similar analysis at the rate of 1 tablespoon per hill 1 week after blossoming begins. Make a second application 3 weeks later.
Insufficient pollination may also be a factor. Are you or neighbors using insecticides heavily? Has your area been affected by the decline in kept honeybees and natural insect pollinator populations? In terms of pollinators you can "keep", bumble bees are excellent pollinators of cucurbits, and honeybees will work the flowers as well.