Squash plant with male flower. Photo: extension.unh.edu
Question: I think something is wrong with my squash plants. They produce only male flowers.
Answer: Just be patient: the female flowers will come.
Squash such as zucchinis and pumpkins, as well as most other cucurbits (cucumbers, melons, watermelons, etc.), produce unisexual flowers—separate male and female flowers—on the same plant.
The two can be readily told apart by ovary in the form of the future fruit (round, long, crookneck, etc.) found at the base of female flowers. Only female flowers. The males have no ovary and produce, of course, no fruit, but are vital as they provide the pollen needed by the female flowers to produce fruit.
Ma Nature produces male flowers first to start to attract pollinators. Producing male flowers requires little energy and they are produced abundantly. Each lasts but a day, but new ones replace them. So, after a few weeks of male-only flowers, pollinating insects such as bees will hopefully have become accustomed to visiting the flowers daily to pick up pollen and nectar. That way, when the first female flowers appear, there’ll be bees ready to pollinate them.
So … just wait. The female flowers are on their way!
In the Absence of Pollinators
But what if you’re not seeing bees visiting your squash flowers? First, you do have to look in the morning: squash flowers are pretty much morning bloomers. And adverse weather—heavy rain, extreme heat, unusual cold, etc.—can keep bees away. Also, don’t water on mornings when the plant has female flowers … or if you do water, water only the soil, not the blooms. With that female flower only opening for one day, you do not want to discourage pollinators on that one occasion!
It takes up to 12 bee visits to properly pollinate a squash flower. If bees are not visiting regularly, you have a problem, as improperly pollinated fruits will abort and drop off.
That’s why hand pollination is useful and may even be necessary. In fact, many gardeners find they obtain earlier and more numerous fruits when they hand pollinate, largely because that way, more pollen is applied and therefore fewer fruits abort. Read Be Like a Bee and Pollinate Your Curcubits to learn how to hand pollinate your squash flowers.