There's nothing more frustrating for a vegetable gardener than having nice big healthy squash plants but no squash! The main reason for this problem is a lack of sufficient pollination. Gardeners have depended on bees and other pollinators to pollinate blossoms in their gardens for centuries. In recent years, as bee populations in some areas are declining for various reasons, including suburban sprawl, colony collapse disorder, and changing weather patterns, some plants may need human help with pollination.
Pollination can also be affected by long stretches of rainy or cold spring weather, or watering too vigorously when pollen is forming. Water at the base of the plant by the stem and try to avoid pouring water on the forming blossoms, or early in the morning when the blossoms have just opened.
Many gardeners also try to protect their squash plants from squash vine borers, a pest that can decimate squash crops, by placing row covers over the plants. While very effective if used correctly in protecting from borers, bees cannot access the flowers, leaving pollination in the hands of the gardener.
It is possible to hand pollinate summer squash like zucchini, winter squash like butternut or pattypan, pumpkins, melons, gourds and cucumber plants for better yields. Indeed, the individual flowers for most of these plants only last for a day, so hand pollinating is often necessary for a good yield. This method will also produce an earlier harvest by encouraging plants to grow fruit sooner and faster than waiting for pollinators.
Planting bee-friendly plants can help attract more bees to help pollinate your squash, but you may want to intervene. This article offers some instructions and advice for effectively self-pollinating your squash plants.
Identifying Male and Female Squash Flowers
Wait to hand pollinate until you have a decent number of blossoms on your plants; at least three or four on each plant. Your squash plant will have male and female blossoms. Here's how to tell the difference. The male flower has a bare stem below the flower, while the female flower has a tiny immature fruit: a baby squash! If that female flower is not pollinated, that tiny fruit will drop off and no fruiting will occur.
Sometimes the earliest flowers to appear are male flowers; be patient! Within a few weeks this balance will shift. Female flowers with tiny fruits should appear soon enough. Normally bees will transfer pollen from the male flowers to the female flowers. However, you may need to help nature along by hand pollinating the flowers.
Different varieties of squash have different ratios of male to female flowers. Also the inside of the flowers are a clue to identifying male and female blossoms. The main difference is that male flowers have anthers (little appendages; hey, this is squash sex we're talking about!), which contain pollen (the substance that pollinates) and the female flowers have stigmas--bumpy structures that cluster around a central opening--which receive the pollen.
Pollinating the Female Squash Flower
Mid morning is probably the best time to pollinate your squash, as the flowers should naturally open by then, But if they have not opened yet, you can gently peel them open with your fingers separating the petals and exposing the anthers and pistils.
Pollinating your squash blossoms by hand is very easy, although somewhat time-consuming if you have a lot of squash plants. Simply take the male flower, gently remove the petals, and expose the anther with pollen. You'll need to pick the make squash flower to be able to apply pollen from the anther to the female flower's stigma. Lightly brush the anther against the stigma a few times in the female flower, leaving some pollen behind. Each male flower can pollinate about 5 female flowers. If desired, you may also use a cotton swab or a small paint brush to transfer pollen from the anther to the stigma. You don't need to pick the male flower in order to do this, but these these won't produce squash anyway. Squash blossoms are edible too. You may choose to put your extra squash blossoms into a salad, or make fritters. You can also leave the male flowers on the plant for a little while for the bees to gather nectar from.
That's all there is to it. Now you can sit back and let your squash grow. Be sure to pick summer squash when they're small, for the tenderest flesh. A zucchini can go from six inches long to a foot long practically overnight, if there is enough sun and rain. Happy growing!