Tons of blooms have been all over my squash and cucumber vines but they have not been producing vegetables. What's the cause and how I can avoid this problem in the future?

Pumpkins, cucumbers and squash are examples of plants that have separate male flowers and female flowers. In order for the plants to produce fruit, the female flowers have to be pollinated—the pollen from the male plant needs to contact a receptive female plant part. There are a few problems that will affect pollination and thus fruit production.

One problem is the lack of pollinators. Wind, rain and insects are the most common pollinators. The most important pollinators are of squash plants however are honeybees. The pollen is sticky; therefore, wind-blown pollination does not occur. Honeybees are the principal means by which pollen is transferred from the male to the female flower. Other insects cannot be depended upon for pollination. Farmers who grow these crops place hives of bees In their fields to insure that pollination takes place. Recently, honeybee populations have decreased because of a combination of two deadly viruses that kill bees, and the overuse of chemical insecticides as well as mysteriuous conditions like Colony Collapse Disorder. And of course, wild honeybees can be rare in some urban neighborhoods, and when bees are absent, fruit set on garden plants in the cucurbit family is very poor and often non-existent. If only a few bees are present in the area, partial pollination may occur, resulting in misshapen fruit and low yield.

If insect populations are low and we have cloudy skies or heavy rains during the flowering period, pollination will be greatly reduced because honeybee activity is reduced. In addition, periods of high heat and humidity during flowering will cause flowers to drop off or to not set fruit.

When no bees are present in the garden or the bee population is
too low for good fruit set, you can substitute for the bee by pollinating by hand. Hand pollination is a tedious chore, but it is the only means of obtaining fruit set in the absence of bees. The pollen is yellow in color and produced on
the structure in the center of the male flower. You can use a small artist’s paintbrush to transfer pollen, or you can break off a male flower, remove its petals to expose the pollen-bearing structure, and roll the pollen onto the stigma in the center of the female flower. When hand-pollinating, it is important to use only freshly opened flowers. Flowers open early in the morning and
are receptive for only one day.

The female flower in cucurbits can be recognized easily by the presence of a miniature fruit (ovary) at the base of the flower. Female squash flowers are much larger than the female flowers on melon and cucumber plants. The male squash flower can be identified by its long, slender stem. The female squash flower is
borne on a very short stem.
In melons and cucumbers, male flowers have very short stems and are borne in clusters of three to five, while the females are borne singly on somewhat longer stems.

Gardeners often become concerned when many flowers appear early, but fruits fail to set. The reason for this is that all of the early flowers are males. Female
flowers develop somewhat later and can be identified by the miniature fruit at the flower base. In hybrid varieties of summer squash, however, the first flowers to appear are usually females, and these will fail to develop unless there are male squash flowers -- and bees -- in the nearby area.

The female flowers are the ones that have a swollen area at the base of the flower.

In addition, periods of high heat and humidity during flowering will cause flowers to drop off or to not set fruit. Adverse weather conditions will also prevent the fruit from maturing; the tiny fruits will yellow and drop before they get a chance to develop.

You can help to ensure that your plants pollinate well, whether the flowers are imperfect or perfect with a few cultural practices. Reduce the use of insecticides in your garden. Insecticides do kill those “bad” bugs that damage your plants, but they also kill the “good” bugs like bees that move from plant to plant pollinating as they go.

There are no panaceas though, no easy sprays that you can apply to the plants to ensure pollination.