Gardening Pollination Vegetables

Only Male Flowers on Cucurbits? Give It Time!

By Larry Hodgson

If you’re fairly new at home gardening, you may find growing cucurbits (cucumbers, squashes, melons, etc.) a bit exasperating. The first flowers that appear are male ones. They open beautifully, giving you hope of fruits to come, then fall off without producing anything. Frustrating!

But don’t worry: this is all part of Mother Nature’s plan. 

The “Male First” Strategy

Producing male flowers requires comparatively little energy, so the plant usually generates them abundantly and early. Early so as to create a habit among visiting bees, because cucurbit flowers are not all that attractive to most pollinators. By producing male flowers in increasing abundance early in the season, and producing fresh flowers every day, the plant assures that pollinators get into the habit of including the flowers in their daily routine. And early in the day, too, since cucurbit flowers last only one day and have already faded by late afternoon. 

Comparing male and female squash flowers.
Male squash flowers (above); female flowers (below). Abrahami, Wikimedia Commons

That way, when female flowers start to appear (you’ll recognize them by the ovary in the form of the future fruit at their base), pollinating bees will be used to visiting the cucurbit patch daily and will be less likely to balk at visiting female flowers, which aren’t as attractive as male blooms since they only offer nectar to bees (male flowers load them with both nectar and pollen). 

So, now you know! 

The Cucamelon Goes Its Own Way

Cucamelon fruits: tiny but tasty. Photo: Corey Ryan Hanson, Wikimedia Commons

The above applies to most cucurbits: squash of all kinds (and that includes pumpkins, zucchinis [courgettes], pattipans and many more), cucumbers, watermelons and melons, especially: they all produce male flowers first. Oddly enough, though, there is at least one cucurbit that does things differently. 

Female cucamelon flower with visiting bee.
Cucamelons produce only female flowers at first. Notice the ovary at the base of this female flower. Photo: Nadiatalent, Wikimedia Commons

The cucamelon or mouse melon (Melothria scabra) produces female flowers first and only after a few weeks of daily female blooms do the first male flowers show up … followed, of course, by the first mature fruits, because from that point on, pollination becomes possible. 

Why does it do this? I don’t know, but that’s the way it works.

In North and South America, squash bees (Peponapis spp. and Xenoglossa spp.) are the main pollinators of squash flowers (Cucurbita pepoC. moschata and others), followed by bumblebees. Honeybees are not great pollinators of squash: apparently, they find their pollen too heavy, sticky and spiny.

Squashes are only native to the New World and squash bees co-evolved with them. As a result, squash bees are not found in Eurasia, Africa and Australia and are likewise absent from many islands. In those places, other bees have to step in and carry out squash flower pollination.

Squash bee visiting squash flower
Squash bee (Peponapis pruinosa). Photo: USDA ARS

Three other weird facts about squash bees:

  • They’re stingless.
  • They often spend the night in wilted squash flowers.
  • They’re specific to squash and don’t normally visit the flowers of other cucurbits, notably watermelons, cucumbers and melons.

3 comments on “Only Male Flowers on Cucurbits? Give It Time!

  1. The extra male flowers are good for frying though.

  2. jilldoner

    link doesn’t work

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