JULY
2005

 

 

 

By
B. Rosie Lerner
 
Extension Consumer
Horticulturist
Purdue University

 

 

 

 

 

07-21-05

Squash Blossom Drop

A common complaint among vegetable gardeners is that their squash plants have a lot of flowers, but many of them just fall off without producing any fruit. This same observation can be made of cucumbers, melons, pumpkins and gourds, all of which are collectively known as "vine" crops to home gardeners. These plants are all members of the Cucurbitaceae family and are also commonly referred to as "cucurbits."

All of these vine crops produce separate male and female flowers, but usually there are both types on the same plant. In order for a fruit to be produced, pollen must be successfully transferred from the male flower to the female flower. In the garden, pollen transfer is conducted primarily by bees. If pollen does not successfully unite with the egg cells within the female flowers, then no fruit will be produced and the female flowers will abort.

It is easy to tell the difference between female and male flowers in this group of plants. Female flowers look as if they have a miniature fruit (squash, cucumber, gourd, etc.) just below where the petals are attached. Male flowers simply have a slender stalk below the petals.

If the male flowers are the ones falling off, this is normal! Often, the very first flush of flowers early in the growing season will only be males, and, of course, these male flowers are expected to fall off after pollen is shed. The next flush of flowers should include both male and female flowers.

However, if female flowers are the ones dropping, then it is safe to conclude that some factor is preventing successful pollination. The most common culprits include excessively hot or cold temperatures and lack of bee activity due to weather, low population, etc. Some commonly used insecticides, including carbaryl (Sevin), are highly toxic to bees; so if you must apply such products, try to time your sprays for periods when the bees are not active.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox