February 27, 2023

Reading time: minutes

Once you know how to tell a male pumpkin flower from a female one, it's a simple matter to hand pollinate your female flowers and be sure of more pumpkins, especially in rainy weather when pollinating insects aren't on the job. (Or your pollinator population has been decimated by pesticides.)

Today's short post is part show and part tell, and it covers:

  • what male and female pumpkin flowers look like, 
  • how to hand pollinate your pumpkin flowers, and 
  • why you might want to.

Boy flowers and girl flowers on the same plant

Pumpkins and other Cucurbits (like zucchini, squash, gourds, cantaloupes) are monoecious, which means they have separate male and female flowers on the same plant.

In order for a female flower to produce a fruit, it needs to be pollinated with pollen from the male flower. Pollinating insects will obviously do this for you, but in rainy weather or if you have a shortage of pollinators, hand pollination is a simple and easy solution. (Although I also encourage you to consider how you can support your pollinator insect populations as much as possible!)

Telling girls from boys 

Some years ago our friends' young children were visiting to play with our young children and my friend later told me that her daughter had come home and said, "Mummy, I know how to tell boys from girls." 

"Really? What kind of boys and girls?" 

"Pumpkin flower ones!"

Most homegrown food and medicine is so simple a small child can do it, and this is certainly the case with pollinating pumpkins. In the image up the top you can see the swelling at the base of the female flower on the right. In the image below, you can see the multiple headed stigma in the center of the female flower on the left and the single stamen in the male flower on the right.

As another friend said when I was first learning about this, "it's pretty obvious which is male and which is female."

view from above showing single stamen in male pumpkin flower and multiple headed stigma in female flower

Hand pollinating 

So the next question is what do you do with these male and female flowers?

In a perfect world all you'd have to do is sit back and admire them, and feel gratitude for and wonder about the pollinating insects busily carrying pollen about with them. But in wet weather (which for obvious reasons reduces insect activity), or if you have a shortage of pollinators, you might want to lend a hand. 

In the picture below you can see the male flower removed from the plant, and then in the next picture with its stamen separated from its petals.

(You can eat the petals of the male flower while you do your pollinating, or bring them in and put them in a salad. Or if you don't want to destroy the male flower, collect some of its pollen with a cotton wool bud or a paint brush.)

Image of a male pumpkin flower separated from the plant for hand pollinating.
Image showing male pumpkin flower with the stamen removed for hand pollinating.

Whether with the broken off male stamen or with a cotton wool bud or paintbrush, transfer some pollen to the multiple headed stigma in the center of the female flower. You'll see the powdery pollen on the male stamen and if you look closely you can see some of it transfer to the female flower.  Be thorough: brush a little pollen onto each of those little curving female parts.

female pumpkin flower ready for hand pollinating

Below, you can see a pumpkin forming from a successfully pollinated flower on the left, and one that missed out on the right.  The flower that was not pollinated had already fallen, and the browned off swelling from its base also fell when I brushed against it. Watch out for these browned off female flower swellings -- they indicate inadequate pollination in your pumpkin patch.

mage of a pumpkin forming on the left and an un-pollinated flower that has died, on the right

Making a hat 

We live in an area that can be very wet, so after hand pollinating, to prevent the newly pollinated female flowers from filling with rain and possibly failing to set fruit, sometimes I give them a hat. 

In the picture below I've broken off a large leaf and...

Image showing pumpkin vine with one large leaf broken off to protect a hand pollinated female flower from rain

positioned it over the female flower as a rain hat, and...

Image showing pumpkin vine with one large leaf broken off and positioned over a female flower to protect it

brought its stem together with the stem of a leaf above to make it less likely to fall or blow away. (Same leaves. Sorry about the change in color from the last picture to this one... the sun must have come out or something. Photography isn't one of my strengths.)

3rd image showing pumpkin vine with one large leaf broken off and positioned over a female flower to protect it

A decent breeze would mess up my nice architecture of course, but it only needs to stay put for a day or so. 

When do female flowers open, and for how long?

Pumpkin flowers begin to appear when the vine is about 50-55 days old. The male flowers start opening about a week before the female ones, so if at first you see only males, don't panic -- the girls will be along soon. There are always more male flowers than female, and the female flower opens in the morning and will close by afternoon or evening. 

So it's worth paying a visit to your patch every morning to pollinate open female flowers and take note of where new ones are forming. In the picture below, I've circled immature female flowers in yellow and males in orange.

image showing male and female flowers unopened

Where to put the pumpkin patch?

I used to think of pumpkins as a plant that belonged in a out of the way spot where it could be comfortably messy and no-one would see the mess. Now, I keep our messy pumpkin patch right beside our most used path, within easy view of the porch -- because that way I see the flowers each morning and remember to go out to the patch to pollinate. 

Those brief pollinating moments usually lead to further moments out in the garden that I might otherwise not have indulged in -- and all of that is good for the soul and also for the kitchen table.

Please comment...

Tell me about your pumpkin patch? Any tips for growing or using pumpkins, pumpkin seeds, or flowers?

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  • My self-sowed pumpkins grow like Jack’s beanstalk. I can’t keep them in line. The paths, compost heaps and plants are over-run in 3 or 4 days. Some vines are 8cm thick. I’ve been eating the fruit small, like a marrow. Delicious!

    • 8cm, wow, that sounds amazing 🙂 Thanks for commenting, Jennifer!

  • I do hand pollinate and wondered why the female sometimes failed to grow; so, now shall provide a leafy hat. My big problem this year and last year is powdery mildew. I’m in Toowoomba, Qld.

    • Hi Dana, I’ve lived near Toowoomba on a couple of occasions and have fond memories of it; what a beautiful area.

      I’m not sure what could be causing your flowers to not produce after having been pollinated unless it is because of rain after pollination in which case hopefully the rain hat will help. (I’m guessing you are already making sure some pollen from the male flower gets onto each part of the stigma in the female flower.)

      Powdery mildew can be a problem for us, too, in our very moist climate. It affects zucchinis, cucumbers, and melons and makes them quite difficult for us to grow.

      But our pumpkin vines seem immune to it and I wonder if that’s because they’re essentially feral — they come up all over the place from both pig manure in our animal areas, and from missed pumpkins that have spilled their seeds in our garden areas. I never plant pumpkins on purpose; I always welcome them and make space for them where-ever they volunteer to grow. So I wonder if they’re self-selecting towards being able to thrive in our specific conditions? I don’t know if that idea might be helpful for you to play with?

      They seem to come up in different areas over time, too, which probably helps.

      I’ve found that for us, starting from seed and then transplanting them isn’t a good idea; it always seems to result in weak plants that don’t really get going. I know frosts can be heavy in your area; I wonder if starting seeds in the soil under frost protection might help to give them a head-start without having to start them indoors and then transplant them…

      I also know, as I am sure you do too, that they’re very heavy feeders. Maybe they need to find a home in a compost pile or manure pile, to enable them to get going more vigorously so that when the mildew hits, the vines are already strong?

      And finally the last thought that occurs to me has to do with diversity… our gardens are a mess, full of all sorts of “weeds” and odd jumbles of grasses and other plants as well as our food plants. I don’t know if this would help specifically with powdery mildew–probably not–but it would help with general vigor which i think is probably the key to our success. It’s certainly not diligent management that’s doing the trick!

      Any way, Good luck! and I would love to hear back if you figure out the solution and feel like sharing 🙂

      All the best

  • Raymond [Ray] Bennett says:

    A very clear and explicit explanation. Thank you.

    • You’re welcome, Raymond, and thanks for commenting.

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