Why a Zucchini Flowers But Does Not Produce

Written by Jenny Green; Updated December 14, 2018
Why a Zucchini Flowers But Does Not Produce

Why a Zucchini Flowers But Does Not Produce

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Fruits should naturally follow flowers, so it's frustrating when a zucchini (Cucurbita pepo var. cylindrica) is covered in blooms, but refuses to follow through with its delicious cylindrical fruits. Zucchinis are summer squashes that grow during frost-free seasons in U.S. Department of Agriculture plant hardiness zones 2 through 11. If your zucchini plant is flowering, but doesn't produce any fruit, you may only have to wait a while for the plant to mature or for the weather to change. Alternatively, your plant might need a helping hand with pollination or cultural conditions.

Only Male Flowers

Zucchini plants produce male and female flowers on the same plant, but a young plant may only be producing male flowers and not the female flowers that develop into fruit. Both types of blooms are large, yellow and trumpet-shaped. However, the stem of a male flower is long, slim and straight, while the stem of a female flower is shorter and has a bump at its base, which is the unpollinated fruit. Young zucchini plants often produce only male flowers for the first week or so, resulting in no fruit set. If your plant is young, it may only be a matter of time before you see fruits beginning to grow.

The Weather's Too Hot

If daytime temperatures are over 90 degrees F and nighttime temperatures are above 75 degrees F, your zucchini plant could be dropping fruits before they have a chance to develop. You can help mitigate this effect during spurts of high temperatures by watering the plant regularly so the soil doesn't dry out.

Pollination Failure

Honeybees are the main pollinators of zucchini flowers. The male and female flowers grow in different locations on the plant, and the bees transfer the pollen from the male to the female flowers. If your local area is deficient in bees, this could be the reason your zucchini plant doesn't produce any fruit. Hot weather can also cause pollination failure. High temperatures reduce pollen germination, resulting in incomplete pollination of the female flowers and misshapen fruit.

You can help Mother Nature by pollinating the female flowers yourself. To transfer the pollen, which looks like yellow dust, dab the center of a male flower with a small paintbrush, and then dab the paintbrush in the center of a female flower. You can also pinch off a male flower, remove its petals and gently rub its center into the center of a female flower.

Cultural Care

A zucchini plant requires fertilizer to produce plenty of fruits. Apply a nitrogen fertilizer to the soil around your plant at a rate of 1/2 cup of 46-0-0 fertilizer or 1 cup of 27-3-3 fertilizer per 25-foot row in midseason, when the plants are fully grown. Sprinkle the fertilizer over the soil about 6 inches away from the main stem and water it into the soil. Zucchini also requires 1 inch of water per week, either from rainfall or irrigation. Don't overwater your plant, however. Soggy soil can cause developing zucchini fruits to rot. Spread a layer of straw mulch about 2 inches deep under the plant to prevent the fruits from coming into contact with damp soil.

Parthenocarpic Zucchini Varieties

In areas where bees aren't common, parthenocarpic zucchini varieties often provide the solution to unpollinated female flowers. Parthonocarpic plants produce female flowers that don't require pollination for fruit development. Zucchini varieties that are parthenocarpic include 'Dunja,' 'Plato' and 'Bush Baby.' Read zucchini seed packets to find other varieties.

About the Author

Jenny Green


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