How to Pollinate Squash by Hand (And Why Your Plants Have Lots of Flowers But No Fruit)

Have you ever wondered why your squash plant is full of flowers but no fruits? Or tiny fruits that keep rotting and falling off the vine? The problem isn’t pests or diseases—it’s the birds and the bees (or lack thereof). Learn how you can hand-pollinate squash plants yourself in the absence of pollinators and multiply your harvest.

Linda Ly

Written by Linda Ly

The sex life of squash: why your plants have lots of flowers but not fruits

“Why does my butternut squash start to rot before it grows any bigger?”

Or, “How come I have lots of flowers on my zucchini plant but never get any fruit?”

These are the questions that plague gardeners every summer, and they’re often blamed on irrigation, pests, or diseases, when in fact they could very well be blamed on the bees (or the insecticides that keep them from coming around).

How so?

You see, a squash plant has both male and female blossoms on its vines (in plant lingo, this is called a monoecious plant) that show up at different times.

In heirloom varieties of squash, the males usually appear first, growing in abundance on the end of long, thin stems. Females usually appear first in hybrid varieties of squash, but sometimes this is all dependent on the weather.

Long days and warm nights tend to favor male flowers, while shorter days and cooler nights favor female flowers. So you often see male flowers in the beginning of the season, a balanced mix in midsummer, and gradually more female flowers as the season comes to an end.

Squash plant laden with male and female flowers
Squash plant with lots male and female flowers—can you tell which is which?

Male flowers tend to be rather large and showy, flaunting their stuff before the females arrive. The males vastly outnumber the females, and if squash could take out personals ads, there would be lots of them from single males looking for females!

Young male squash blossom
A young male flower—notice how it grows from a long, thin stem
Mature male squash blossom
Mature male flower
Male squash flower
Male flowers are always large and showy compared to female flowers

Female flowers usually appear a week or two after the males, growing low to the ground and close to the vine.

They form with what look like miniature squash between the flower and the vine. This is the ovary, as the female always bears the baby. The ovary is essentially an immature squash awaiting pollination (fertilization) by the male flower. Without it, that baby will never grow beyond the size you see.

Squash vine with female flowers bearing immature fruits
Female flower with an immature squash
Female zucchini flower with ovary (immature squash)
Female flowers grow low and close to the ground
Female pattypan squash flower
If this female flower isn’t pollinated, that baby squash will rot off the vine

If the ovary is not pollinated when the female flower opens in the morning, the flower will close that evening, start to wither, and eventually fall off the vine in a few days. That means no squash will come, even if it looked promising at first.

And yes, that means female flowers only open for one day, so all the stars have to align for those flowers to be pollinated properly!

Non-pollinated female squash blossom with shriveled petals
An unpollinated female flower
Unfertilized female squash flower and rotting fruit
Unpollinated female flowers will turn brown and fall off the vine

If a bee (or other pollinator) happens to come around that morning, you have to hope that it does a good job of spreading the pollen around so you get some squash. It can take up to 15 honeybee visits to achieve pollination, versus 6 visits from a squash bee and as little as 2 visits from a super efficient bumblebee.

Bees land inside open male flowers to collect nectar and with all their activity, they also happen to gather pollen on their bodies. As they buzz around the plant, keeping busy and doing what bees do, they may land inside an open female flower and unintentionally transfer pollen to it.

That’s right—your next meal wholly depends on these little creatures finding your squash flowers amongst thousands of other flowers in the neighborhood and unwittingly fertilizing them.

If there isn’t enough pollen to pollinate the female flower, the ovary on that flower won’t be fertilized. Since it sometimes takes many bees to pollinate your female flowers and turn them into squash, this is all the more reason to attract as many bees as possible to your garden with beneficial, nectar-rich plants.

When bee activity is low, some gardeners will take the extra step of hand pollinating their flowers to help them along.

Even if you have a healthy bee population in your garden, you could try hand-pollinating a few blossoms just to increase your overall yield. You might be surprised at just how many flowers don’t end up getting pollinated naturally!

Close-up of stigma inside a female squash blossom

How to pollinate squash by hand

First, get yourself familiar with squash blossom anatomy.

On a male flower, the stamen is the reproductive structure in the center, consisting of an anther (the pollen producer) supported by a thin filament. This phallic anther is what you see covered in yellow pollen grains.

Close-up of anther inside a male squash flower
Anther on male squash flower covered in yellow pollen grains

On a female flower, the pistil is the ovule-producing structure, consisting of an ovary (immature fruit) that supports a long style, topped by a stigma (a sticky orange structure in the center). This stickiness is what helps the pollen adhere to it.

Close-up side view of pistil with sticky orange stigma on top
Pistil on female squash flower with a sticky orange stigma

Remember that male flowers grow on tall, skinny stems, and female flowers grow close to the vine with an immature fruit at the base.

During hand pollination, you’re simply mimicking the bees by collecting pollen from the anther and depositing it onto the stigma. Yes, it’s as easy as it sounds!

The ideal time to pollinate squash is in the morning as soon as your squash blossoms open (and temperatures are mild). They tend to close up by early evening, so you might spend several days pollinating by hand if you want to get to them all.

Hand-pollination method #1: Pick the male flower.

  1. Identify a male flower on the squash plant and make sure it’s fully open, or the pollen won’t be ripe. (You’ll know pollen isn’t ripe when you rub the anther with your fingertip and no grains come off.)
  2. Pick the male flower; you’ll be using it as your “tool” to fertilize the female flowers.
  3. Peel back (or strip off) the flower petals to reveal the anther. Gently rub the anther onto the entire surface of the stigma (of your female flower) until it’s sufficiently pollinated. Be sure to work quickly, as pollen only remains viable for a few minutes after it’s taken from the anther.
  4. Repeat with as many male flowers as needed to pollinate all the female flowers.

Hand-pollination method #2: Use a paintbrush.

  1. Using a soft, small paintbrush, lightly brush the anther of a male flower until the bristles are covered in pollen.
  2. Brush the stigma of a female flower a few times (as if you’re painting it).
  3. Gather more pollen from other male flowers with your paintbrush and continue “painting” stigmas until all the female flowers are pollinated.
Stigma on a female squash flower after pollination
Female flower with the stigma exposed

Some people use a Q-tip or other cotton swab to hand-pollinate, but from personal experience, I’ve found that a lot of the pollen sticks to the fibers (resulting in not as much pollen transferring to the stigma).

Once pollination is successful—you’ll know in two to three days and it’s almost a sure bet with hand pollination—the ovary begins to swell and mature into a seed-bearing fruit. And within a few weeks, you can harvest that squash!

If pollination did not take, cut off the rotting fruit. It will never develop into anything, and leaving it on the vine is an energy drain on the plant (not to mention a landing pad for pests).

As for the male flowers? Well, if they’re not harvested for food or picked for hand-pollination, they die off soon after they open. So don’t let them go to waste!

Related: The tops and tails of these vegetables are edible—and you didn’t know it

Why pollination may fail

While hand-pollination is almost always successful, a few things can hinder your efforts. Proper pollination depends on good pollen, and good pollen depends on temperature, sunlight, hormones, and plant maturity.

Male squash flowers growing on long, thin stems
These male flowers are still too young to pollinate female flowers
Male squash blossom
This mature male flower will have viable pollen

Daily temperatures that are too high can affect the quality of the pollen (even turning it sterile). While squash is a warm-weather crop, extreme heat (daytime temps over 90°F or evenings that never fall below 70°F) can reduce pollen viability.

Consistently hot weather may also mean lots of male flowers but much fewer female flowers to pollinate (and fewer chances of getting fruit).

Heavy rain or excessive overhead watering can also reduce the amount of pollen available, which is one good reason to opt for drip irrigation in your garden beds or soaker hoses to water your plants more efficiently. If you must water by hand, water only the soil (not the blooms) and don’t water in the morning when the female flowers open—you don’t want to discourage pollinators from visiting!

Female squash blossom with immature fruit attached
Water your squash plants when the female flowers are still closed

What to do next with your squash harvest:

This post updated from an article that originally appeared on July 16, 2014.

Linda Ly

I'm a plant lover, passionate road-tripper, and cookbook author whose expert advice and bestselling books have been featured in Time, Outside, HGTV, and Food & Wine. The National Parks Cookbook is my latest book. Garden Betty is where I write about modern homesteading, farm-to-table cooking, and outdoor adventuring—all that encompass a life well-lived outdoors. After all, the secret to a good life is... Read more »

40 Comments

  1. Fantastic information. I have seldom had great luck with zucchini squash. Now I know what to do. Thank you!!!

    Reply

  2. I use your tomato plant concoction and I get great results. My tomato plants are a foot taller than my neighbors. He is a little cranky about it. What does the aspirin do.
    Dennis

    Reply

  4. Why don’t any of my 32 tomato plants have flowers in July? They were planted in May. I live in North Carolina. Most of the plants don’t even have fruit.

    Reply

    1. It’s hard to answer this without knowing other details like the specific varieties planted, their days to maturity, your climate zone, how much and what types of fertilizers were used, etc.

      Reply

  5. This is great, very helpful. Thanks.

    Now, a comment about the information architecture you’ve chosen, and its usability. I have a large monitor, yet the information I was *actually* looking for, as promised by your headline, was buried 17 screens down. That is a LONG way to scroll.

    A very short list of relevant sub section links at the top would make your site far more usable and enjoyable. As much as I appreciate your work, this flaw irritates me greatly. And if me, then others.

    (street cred: I’m a UX designer with 33 years of experience designing for many of the most iconic companies in Silicon Valley. I don’t mean to brag – my intent is only to add credibility to my observations.)

    Anyway, thanks again for the article, and for a great website. Your advice helped me to nurture a garden that’s exceeding all of my expectations this year. My brown thumb is gone! 🙂

    Reply

  7. Brilliant, as always, and always something to learn from you. Didn’t realize female flowers only last for 1 day if not pollinated. This will also help me respect all those male flowers more. 🙂 Thank you, Linda!

    Reply

  8. So glad you posted this! This is my first year of growing squashes and my plants are full of flowers. I would have been disappointed if we didn’t get any pumpkins for Halloween.

    Reply

  9. I love how your posts are always so packed full of useful information 🙂 So what are the flowers that are usually eaten? Male or female or both?

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    1. We usually eat the male flowers since there’s so many more of them (and we don’t have to sacrifice any fruit). But occasionally, farmers’ markets will sell the female flowers with baby squash still attached.

      Reply

  10. This is a great post! I briefly read about the sex life of squash when I was dumbfounded why all my squash plants weren’t producing fruits. I loved this in-depth coverage of the process… thank you!

    Reply

  12. Is it weird that I find this crazy interesting? After reading this, I’ve been plotting all day on how to attract more pollinators…

    Reply

    1. Not weird at all, I geek out on this kind of stuff all the time! The process of pollination fascinates me.

      In my garden, the bees are most attracted to flowering herbs. I have a small bed of basil that grows year round http://gardenbetty.com/2011/05/african-blue-basil/ and at any given time, there are dozens of bees hovering over those three (large!) plants. They also love flowering rosemary, parsley, cilantro, dill, and thyme. Some of these herbs are perennial while others are “wild,” as I let them reseed every season.

      Reply

    1. This year I had sunflowers growing near my squash to up the bee activity. Flowering herbs (basil, parsley, cilantro, dill) also attract them.

      Reply

  14. Wonderful and in depth post. I love the photos. I would also like to add, that you have a better chance of proper pollination if you have multiple plants. This way a bee can jump from flowers on one plant to another and increase chances of fruit … same plants of course.

    Reply

  15. Great discussion. I wonder if the female flower only opens for that one day. Interesting to ponder.

    Reply

    1. As far as I know, the female flowers only open once. The males may open a second time before they die, but the pollen won’t be viable. Such a game of chance and luck, huh? Once I learned this, it made me truly treasure the squash I DO get!

      Reply

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