Lawn & Garden Advice for Northwest Florida

Cucumbers & squash not setting fruit

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Q. I have problems growing cucumber, squash and watermelon. They wonít set fruit even though the plants appear healthy. What am I doing wrong?

A. More than likely this is the result of incomplete pollination. Itís quite common in the cucurbits, which include cucumbers, squash, cantaloupe and watermelon. Plants in the cucurbit family mostly have separate male and female flowers occurring on the same plant. The male flowers produce pollen which has to be moved, usually by bees, to the female flowers. Both the male and female flowers are yellow. But the female flower will be attached to the plant by what looks like an immature cucumber if it is a cucumber plant or an immature squash if it is a squash plant, etc. The male flower is attached to the plant by a thin greenish stem.

Incomplete pollination occurs when there is insufficient movement of pollen from the male blossoms to the female blossoms. In most cases, this means that there were not enough bee visits and, as a consequence, not enough pollen delivered to fertilize enough of the seeds. This will result in the fruit (cucumber, squash, watermelon, etc.) either aborting or only developing partially around the seeds that did become fertilized, producing a malformed fruit. Researchers have found that it takes at least eight honeybee visits per flower to pollinate cucumbers adequately.

In the absence of sufficient bees, you can try hand pollinating of a few plants. This can be done by transferring pollen from newly opened male flowers using a small brush. Then deposit the pollen on the stigma, which is on a raised area in the middle of the open female cucurbit flower. More detailed information on how to do this is available at http://edis.ifas.ufl.edu/hs398.

If you have other problems with your vegetable plants, bring a fresh sample to our June plant clinic. The sample may include the fruit (tomato, pepper, squash, etc.) or plant stem with at least several leaves. For plants that suddenly wilted, it is best to bring in the entire plant including the root system if possible. You may also bring in insects that are believed to be pests for identification and control recommendations. Lawn and landscape plant problems can be diagnosed as well. Itís important to bring a fresh sample that represents symptoms seen. A sample from a lawn should include a 4-inch square of grass with roots attached. The plant clinic will be held Thursday, June 16 from 10 a.m. to 1 p.m. in Fort Walton Beach at the Okaloosa County Extension building, 127 W. Hollywood Blvd.


Larry Williams, UF/IFAS Extension Agent, Okaloosa County, June 8, 2011


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