CORVALLIS, Ore. – Heat-loving squash and cucumber plants will take advantage of hot weather to blossom and set fruit. Successful pollination depends on insect pollinators, such as honeybees and native bees, as well as timing and location.
Sometimes pollinators are in short supply, and Mother Nature may need help.
"This may be a particular problem when the weather is cool and wet," said Jim Myers, vegetable breeder at Oregon State University. "The weather slows down pollinators, and fruit tends not to develop well. This accounts for tapered ends in squash and cucumbers and can lead to a loss of the whole fruit."
Gardeners can pollinate the flowers themselves with a small watercolor paintbrush to lightly transfer pollen from male flowers to female flowers.
Most squash and cucumbers have separate male and female flowers on the same plant, Myers explained. Female blossoms have what looks like a tiny squash or cucumber below the flower. The tiny fruit is the ovary, full of eggs not yet fertilized with pollen from male flowers. Male blossoms have long-stalked stamens, each with pollen-filled anthers. Every pollen grain contains sperm nuclei, which fertilize the ovules in the female flowers.
Don't worry if the earliest blooms on squash or cucumber plants fall off before they set fruit. The male flowers of cucumbers and squash often bloom and wither before the female blossoms start appearing.
Be patient with squash and cucumber plants, Myers advises. Eventually, most will produce both male and female flowers. When blossoms of both sexes are open at the same time and no fruit forms, pollination may be poor.
Research in the OSU horticulture department has shown that many plants attract pollinators and other beneficial insects. The plants include cilantro, yarrow, wild buckwheat, white sweet clover, tansy, sweet fennel, sweet alyssum, spearmint, Queen Anne's lace, hairy vetch, flowering buckwheat, crimson clover, cowpeas and caraway.
When fruit develops, keep the plants well watered. Don't let cucumbers or summer squash get too big – they often get seedy, stringy or tough, said Meyers.