Squash pollination problems

County Agent’s Corner



Q: I was walking in my vegetable garden the other day and noticed that some of my squash blossoms are falling off. What is going on? Is this an insect problem? What should I do?

A. I have gotten several calls recently similar to yours, so don’t feel alone. There are several different issues that may result in blossom drop, but none of them are serious. In fact, your plants may just grow right out of their problem.

Most squash (and cucumbers for that matter) have separate male and female flowers on the same plant. So, it is important to know which flowers are dropping – male or female. In the center of the female flower, you will find several bumpy structures surrounding a central opening. These structures make up the stigma. Also, female blossoms have what appears to be a tiny squash just below the flower.

Male flowers grow on a long narrow stem and contain the stamens. Each stamen grows on a long stalk and has anthers that are filled with pollen. The anthers look a lot like the applicators that are used to apply eye shadow. (My analogy is probably not the best, but hopefully this gives you a good mental picture.)

Now that we have finished the brief plant biology lesson, let’s move on to your problem. If the earliest blooms are the ones that fall off, don’t worry. Often, the male squash flowers will bloom and wither before the female flowers appear.

In this particular instance, patience is the recommendation. Eventually, your plants will produce both male and female flowers and fruit set should soon follow.

Notice that I ended my previous sentence with “should” and not “will.” If both flower sexes are present and fruit set does not occur, you have a pollination issue. Squash pollen is a very sticky substance, so it cannot be transferred via wind like some of our other vegetable varieties.

We depend on insect pollinators, primarily bees, to successfully pollinate our squash plants. Reduced or nonexistent bee populations in your garden directly affect your squash harvest, or lack thereof.

So, is home-grown squash off of your summertime menu if no bees are around? Absolutely not! It will just require a little extra effort on your part. In the absence of bees, squash flowers can be hand-pollinated.

The first step is to find a male flower. Cut it off where the flower stem meets the main stem of the plant. Next, all of the petals should be removed carefully from the flower, leaving you with a stem and exposed anther.

Now, locate a female flower and use your stem and anther to transfer the pollen to the stigma, located in the center of the female flower. Gently rub the anther over the stigma several times, and then move on to the next female flower.

Each anther can be used to pollinate approximately five flowers. Instead of using the anther, you can use an artist’s paint brush to transfer the pollen to the female flower.

No matter the method of pollen transfer, timing is important. Flowers open early in the morning and are only receptive for one day. Be sure to use freshly opened flowers to ensure your hand-pollination success.

Happy gardening!

This column includes research-based information from land-grant universities around the country, including Alabama A&M and Auburn Universities. Email questions to Bethany@aces.edu or call 205-612-9524. Like us on Facebook. Follow us on Twitter. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University), is an equal opportunity educator and employer.