Has squash production stalled on your butternuts, honeynuts, cucumbers, pumpkins, or other squash plants? Learn how to hand-pollinate squash and boost your crop when pollination problems arise.
The very first year I grew butternut squash, I was rewarded with what you could only call Beginner’s Luck. I certainly didn’t do anything to deserve the outstanding harvest that resulted from my accidental efforts.
And the one conscious decision I made that seemed right was also laughably wrong: I planted the seeds smack dab in the middle of my garden, leaving not nearly enough legroom for long, happy vines that climbed everything vertical, including my towering tomato plants.
This location, however, meant the plants would be right on the bee superhighway I had laid through my yard. Fluffy bumblebees and strictly-business honeybees hopped from oregano flower to pepper flower to dahlia to squash flower to lavender, picking up pollen here and leaving pollen behind there.
It was a huge, beautiful harvest.
The following spring, still a bit grumpy from unwinding all the stubborn, prickly vines from my heirloom tomato plants the previous September, I moved the butternut plot to its own little area off to the side. The harvest was okay. Nothing to shout about.
I was more concerned with the fact that squash vines were still gunning for the tomatoes. In a big way, lol. Given the three other directions that the vines could choose to trail, they all went right for the tomato plants some 12 feet away.
Apparently, even butternut squash cannot resist the call of an heirloom tomato.
So, the following year, I moved the butternuts to the front yard in a huge patch recently cleared of ground ivy. There, I thought, they could roam free while leaving my tomato plants the hell alone. Disaster.
By July, I had not one squash, of any size. Flowers, yes. Squash, no.
Some quick research revealed the problem: thinking I had created a better environment for all of my plants, I had, instead, removed the squash flowers from proximity to the bee superhighway in the back yard. The flowers simply weren’t being pollinated.
Most plants in the Cucurbita genus (which includes squash, cucumbers, zucchini and pumpkins) produce both male and female flowers, and depend on insects to transport pollen from male to female into order to set fruit. But with the delicious pollen and nectar smorgasbord going on in the backyard, bees had no interest in exploring the front yard. So, no squash.
I blinked twice at the description of what to do, then went to find the old oil brushes I had abandoned after discovering and confirming my extraordinarily epic ineptitude at painting.
Armed with a paintbrush and tip-toeing through the early morning dew, I suddenly found myself in the curious position of being sex therapist to four butternut squash plants.
But the advice on how to hand-pollinate the squash saved the harvest, and I’m here today to pay it forward. It’s quite common for Cucurbita to struggle with pollination issues, despite [sub]urban legends of zucchini harvests so large that communities lock their car doors at night, lest they find them stuffed to the rearview mirror with excess squash from desperate gardeners.
If your squash production is lagging behind on otherwise healthy plants, a little matchmaking may be in your near future.
First, learn to identify female flowers (above left) and male flowers (above right). The male will always stand atop a narrow stalk, while the female flower forms a squash-shaped ovary in preparation for receiving pollen. In the photo above, notice the baby squash beneath the female flower. This is an unfertilized embryo that will die off if the flower does not receive pollen.
Male flowers will always outnumber female flowers by large margins and usually begin appearing far in advance of the first female flower. This is nature’s way of hedging its bet for successful pollination. So don’t worry if it takes a while to locate a female flower. It’s completely normal.
Cucurbita flowers open in the early morning and wither and close by early afternoon: morning is your only window of opportunity.
With both female and male flowers open, take a cotton swab or small paintbrush and brush along the structure in the center of a male flower (the anther) to collect the pollen on the swab/brush. Squash pollen is bright orange-yellow, and there should be highly visible grains on your swab or paintbrush.
Gently brush the pollen onto the center structure of the female flower (the stigma). You may want to repeat this action with a second male flower, to make sure that the female flower’s stigma is thoroughly covered in pollen.
As an alternative technique, you can also remove the male flower from its stalk, pull off the petals and insert the male stamen into the female flower, ensuring that thorough contact is made between the anther and stigma to transfer pollen.
That’s it! And you may now congratulate yourselves on your remarkable show of restraint in keeping those obvious euphemisms in check during the previous paragraph. I’m proud of you!
I may or may not be blushing a little bit.
In the spring of 2020, my butternuts were maddeningly alternating between all female flowers and all male flowers. And then, when they finally began blooming together, an adorbs American toad took up residence in my squash garden and began eating all of the crawly pollinator bugs that normally would take care of distributing pollen from flower to flower. Crikey.
I wasn’t going to wait it out and hope for the best. On mornings when loads of flowers were opened, I skipped the Q-tip and went straight to the direct route: plucking male flowers, pulling off their petals (see photo above) and carefully rubbing the pollen directly onto the female stigma. One male flower to one female flower. It worked great, and there are now over a dozen healthy, pollinated squash bursting out in growth.
Don’t hesitate to intervene when nature sits down on the job!
These photos (above) are from that long ago third planting in the front yard that I mentioned earlier, when I had spent the late summer hand-pollinating every female butternut squash flower. Left, two female flowers and their butternut embryos wait for their pollen injections. Right, successful pollination sends the fertilized squash into grow mode mere days later, as the butternut sheds its no-longer-needed flower.
How to tell when squash is pollinated
So after all of that work, how do you tell if a squash is pollinated? It will take a couple of days, but the visual signs will be very obvious.
A pollinated squash will immediately burst into growth mode, and will appear plump and bright and be firm to the touch. (Side note: different varieties of butternuts have differently shaded skin tones, so while my honeynuts (above) are a deep green at this young stage, yours might be a pale green.)
An unpollinated squash, on the other hand, will begin to wither and rot away. The blossom end will be noticeably yellow, and the embryo itself will shrivel.
Note that in both cases, the flower will die away, so, a dead or dying blossom is not an indication of pollination status.
One final note: those squash blossoms are a delicious culinary delicacy, but be careful not to pluck too many flowers before your squash have had time to set fruit!
If you’re new to growing winter squash, learn more about my favorite home-gardener-friendly winter squash, the honeynut squash!
- Cotton swab or small paintbrush
- In the morning, look for fully opened squash flowers. You'll need both male and female flowers.
- Examine each open flower: a male flower will sit atop a slender stalk. I female flower will sit atop a mini version of the squash (this is an unpollinated embryo). If there are both open, proceed to the next step. If not, wait until the next day and check again.
- Take your cotton swab or paintbrush and gently, but thoroughly, swipe along the raised nub at the center of the male flower (the "anther"). It should be covered with powdery orange pollen.
- Rub the pollen against the center of the female flower (the "stigma") to transfer the pollen.
- If the pollination was successful, the baby squash will rapidly begin its growth cycle. If not, it will wither and die off. This does not harm the plant.
- It's perfectly normal for squash plants to have many male flowers and few or no female flowers on a given day. Only female flowers will produce a squash; male flowers exist only for pollination.
- Bees and ants are much more efficient at pollination, so, if there are multiple male flowers open on a given morning, repeat the hand-pollinating process of one female flower with a second male flower. It never hurts to hedge your bets.
- As an alternative to using a swab or a brush, you can also pick the male flower and pluck off its petals to expose the anther, and rub the anther against the female stigma to transfer pollen.
- You can cross-pollinate squashes; meaning, you can use, say, zucchini male flowers to pollinate cucumber female flowers (to produce cucumbers). Just don't collect the seeds for replanting, as the next generation will be a hybrid of the two, and will not necessarily be true to variety.