Issue: July 26, 2008
Cucumber plants not making cucumbers
Pruning hail damaged tree
My cucumbers are growing well, flowering, but they are not producing cucumbers. What is wrong?
Cucumber plants, like squash, melons, and many other plants have separate male and female flowers on the same plant. You can recognize the male flowers because they do not have a small fruit behind them. They produce the pollen needed to form the fruit, but they do not produce the fruit. The female flower on the other hand has a small fruit behind the flower even before it opens. The female flower cannot produce the pollen needed to cause the fruit to develop and is dependent upon insect (or human) pollinators to transport the pollen from the male flower.
The male flowers begin forming before the female flowers form. So, it is possible to have cucumbers blooming, but not producing fruit. The time between the first development of male flowers and the female flowers depends on plant variety and environmental conditions. Your problem may just be that the female blossoms have not formed yet. They should be forming soon.
However, if you see the female flowers on your cucumber plants, but they are not "setting" fruit, then the problem may be that you do not have pollinators. In the past several years we have had various problems affecting the honey bee populations. However, bumblebees are good pollinators for these plants. Small, native ground bees are also good pollinators. These ground bees are solitary bees that lay their eggs in holes in the ground. So, even without honey bees you can have successful pollination if you do not do anything to disrupt the other pollinators. However, if you are not getting pollination, there may be something (pesticides or other management practices) that have disrupted the life cycle of the other bees.
If that is the case, and if you are willing to pollinate the cucumbers, you can do it yourself. Each morning collect pollen from the stamens in the center of the male flowers and then transfer that pollen to the stigma in the center of the female flowers. Use a small, soft bristled paint brush to do this. If you are successful, you should see small cucumbers forming within a few days. Leave some female flowers unpollinated (by you) so you can watch for the return of the natural pollinators to relieve you of the early morning effort of pollination.
The change in weather as the rains have come and lowered temperatures should help you by stimulating the development of the female blossoms and by bringing out the native pollinators.
I have noticed a lot of branches in my trees with no leaves on them. We had a hail storm the other day that probably caused this. Can I prune these branches, or should I leave them?
If the absence of leaves on the branches is due to the hail and you have no other reason to remove the branches, just wait and let new leaves form. If these are branches that you need to prune anyway, then you can prune them. This will be less harmful than mid-summer pruning branches with many leaves. That is because these defoliated branches will need to draw stored energy from the branches and trunk to produce new leaves. Pruning before production of new leaves reduces this drain on the stored food reserves. However, minimize the amount of pruning you will do at this time. The leaves, once formed, will begin feeding carbohydrates into the food reserve in the branches, trunk, and roots for growth next year.
Any branches that are dead (dry and brittle) can be pruned now without harming the trees.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: email@example.com, office: 505-865-7340, ext. 113.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!