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Poor pollination may be to blame for scrawny crop

Jessica Walliser
| Friday, Aug. 3, 2018, 12:03 a.m.
Use the center of a male zucchini flower to pollinate three to five female flowers and improve fruit set.
Use the center of a male zucchini flower to pollinate three to five female flowers and improve fruit set.

Q uestion: We have not had very many zucchinis produced yet this year. There seem to be a lot of flowers on the plants, but we’ve only gotten two smallish zucchinis from our four plants. Do you think we got a bad batch of seeds? Or is there something wrong with the plants? Thanks for any insight you can provide.

Answer: If the plants are healthy and producing flowers, it’s not likely that you got a bad batch of seeds. There probably isn’t even anything wrong with the plants. If the plants were producing lots of leaves but very few flowers, I’d suggest a soil test as the problem is most likely an excess of nitrogen in the soil. But, since you have plenty of flowers being produced, a lack of pollination is the most likely culprit.

Like other members of the squash family, zucchini and other soft-skinned summer squash plants produce separate male and female flowers on the same plant. Unlike tomato, pepper or bean flowers, which are “perfect” and contain both male and female parts in each flower, members of the squash family produce gender-specific flowers.

Male flowers, which produce the pollen, have a perfectly straight stalk. Typically, the male flowers are produced first, sometimes a week to 10 days before any female flowers appear. This is to ensure there’s plenty of pollen around when the female flowers open.

Female flowers, on the other hand, have a bulbous base that looks like a miniature zucchini (or acorn squash or pumpkin or whatever you’re growing). These female flowers are open for only one day, and each flower needs to be visited by a pollinator dozens of times in order to receive enough pollen and for the fruit to begin to develop. If you use pesticides in or near your squash patch, bee populations may be impacted, which could lead to a reduction in pollination and your lack of fruit. But, even if you don’t apply any pesticides to your zucchini plants, poor pollination can occur.

Many species of bees, including those that pollinate zucchini, are facing population declines, and I’m hearing from more and more gardeners every season who have the same problem you do. Other than planting lots of flowering herbs and annuals in the vegetable garden to boost pollinator numbers naturally, your best bet is to learn how to hand-pollinate the flowers.

How to pollinate

Hand-pollinating squash blossoms is actually quite easy. The hardest part of the whole affair is the fact that you’ll need to do it first thing in the morning for it to be the most effective, though early afternoon hand-pollination is often effective, too.

To hand-pollinate your zucchini, first locate a newly opened male flower. Cut the entire flower stalk off of the plant. Break off all the petals so you’re left with just the male flower part (the anther) and the stem. It will look like a paintbrush of sorts. Once you have the male flower prepared, find a few female flowers and rub the anther around against the center of the female flower to transfer the pollen. Each male bloom can pollinate three to five female blooms before you’ll have to get a new male flower.

I suggest you perform this task every morning, if possible, or as often as you can, for maximum fruit set. With the help of hand-pollination, you’ll be able to grow plenty of full-sized zucchini.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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