Arrow-right Camera

The Spokesman-Review Newspaper The Spokesman-Review

Wednesday, July 17, 2019  Spokane, Washington  Est. May 19, 1883
News >  Features

In the Garden: Why your hopes were squashed

The pollen from this male zucchini squash flower will be carried by bees to pollinate female flowers so they can produce a fruit. (Susan Mulvihill)
The pollen from this male zucchini squash flower will be carried by bees to pollinate female flowers so they can produce a fruit. (Susan Mulvihill)

Last year, I received quite a few emails from readers wondering why their summer squash plants weren’t producing. Some plants started to develop a squash only to have it shrivel up and fall off. Others looked great and bloomed profusely, but never produced anything. That’s frustrating and annoying for any gardener, to be sure.

One of the most common causes of this problem is a lack of pollination. Perhaps there weren’t many pollinators present in their gardens when daytime temperatures were cool early in the season. This problem usually resolves once the weather warms up.

While that addresses the pollinator aspect of the problem, there’s more to the story and it’s really quite interesting.

Each squash plant develops male and female flowers. The male flowers are usually the first to bloom earlier in the season and can be identified by the thin stem they grow on. The larger female flowers have small fruits at the bottom that won’t develop if the flowers aren’t pollinated. In that case, those fruits will drop off the plant.

But what if a squash plant only has flowers of one sex? It makes pollination impossible and has a lot of gardeners scratching their heads as to how this can even happen.

It turns out that when plants have been exposed to extended periods of cold weather early in the season, it will affect the types of flowers that later develop on the plants. According to research conducted at Purdue University, cooler weather will cause more female squash flowers to develop, well before the male flowers appear. If you think back to the start of last year’s growing season, those are exactly the conditions our plants had to deal with.

You might also be interested to learn that higher temperatures will cause an increase in the number of male flowers.

Another contributing factor that stymies squash production is growing the plants in soil that is high in nitrogen. That will promote lush, green growth but little or no blooming. The plants should be given a fertilizer that is higher in phosphorus than nitrogen.

I certainly wouldn’t want to boast but we had a plethora of zucchini in our garden last summer to the point where it was difficult to keep up with them. That made me wonder why other gardeners weren’t enjoying the same bounty.

Now that I know about the effects of a cold start to the growing season, my theory about why our plants did well revolves around how I started them. I planted the seeds indoors in mid-May. When I planted them out in the garden in early June, I covered their bed with a floating row cover until the plants started blooming a few weeks later.

Row covers let in air, light and moisture while providing the plants with a few extra degrees of protection against chilly temperatures. Perhaps that eliminated the problem of having flowers of one sex although I don’t know for sure. Once the plants started blooming, I removed the cover so bees and other pollinators could do their thing.

I’ll be writing about the particulars of growing winter squash and pumpkins in a couple of weeks but wanted to give you a heads-up about this potential problem so you can consider using row covers. At the very least, it should get your squash plants off to a better start but it just might increase their productivity as well.

Susan Mulvihill can be reached via email at her blog at susansinthe for more gardening tips and information.

Subscribe to the Morning Review newsletter

Get the day’s top headlines delivered to your inbox every morning by subscribing to our newsletter.

You have been successfully subscribed!
There was a problem subscribing you to the newsletter. Double check your email and try again, or email