Why won't my cucumber plants produce fruits?

You may just need to be patient. Cucumbers, like squash, pumpkins, watermelons, cantaloupes, and many other plants, produce male and female flowers separately on the same plant. They often begin producing male flowers several weeks before the females appear. The males make pollen and are necessary, but they do not produce fruits. Look to see if there is a little cucumber behind the flower. If you see a baby cucumber, you have a female flower. If you just see a slender stem going right up to the back of the flower, you have a male flower. If your plants have female flowers and the fruits still aren’t setting, be sure that the plants are not excessively dry. The leaves may wilt on hot days, but they should recover as the temperature drops in the evening. If they are still wilted by morning, you are not watering them enough, or you are watering too shallowly and too often. Excessive nitrogen fertilization also could be a problem. If the nutrients are unbalanced, the flowers will drop. Also, if there are no bees to pollinate your cucumber flowers, you will have to transfer pollen from the male flowers to the female flowers by hand. Use a cotton swab or soft-bristle paintbrush to transfer pollen.