How to tell when to pollinate a female giant pumpkin blossom

Another gardener friend, Mac asked me a great question about the female flower and the timing of the pollination so I thought I’d give you all some more info.

When you spot a female pumpkin blossom that you want to hand pollinate later, you need to watch it daily as it grows.  The optimal position of a female flower will be on the main vine and at least 10 feet out or longer although I did pollinate one this year at 8 feet out for insurance in case no others ‘took’. I will also pollinate every female flower on the secondary vines that grow out from the main vine on the sides. This is all for insurance in case something happens to the best one. Later, after I feel confident which one of these pumpkins is growing the fastest, I will cull all but the first and second fastest growers. So each plant I care about, will have 2 giant pumpkins growing on them. The first and a backup.

Here is a female blossom NOT READY. The blossom is still very green although getting larger.

Here is a female blossom that will be ready to open the next morning. So how do I know when the female blossom will open? I watch the female blossoms closely (they are the ones with the baby pumpkin attached to the base of the flower. I always look for the blossom to get big (still closed) and then the day before, the blossom will get the slightest hint of yellow green on the tip. That’s when I know it will open the next morning. Works everytime. I cover the female flower the night before after the color change and get out in the patch early the next morning.

We have 4 hours from the time the blossom opens which is always first thing in the morning. This is usually between 6am -10am. So I cover the female flower the night before with a piece of row cover and get out in the patch early before the beez take all the pollen from the male flowers. Many times I cover three male flowers that will be ready the next day as well  (they haven’t opened up but look like they will the next day) so I have lots of pollen on them. The beez get out early too and will take it all of their pollen if not covered.  The pollen is food for the bees. It is protein for them. Beez will go after the nectar and the pollen on these plants. I’m sure the beez are attracted to the big blossoms and wonderfully sweet smell the blossoms emit. Someone should make a perfume out of this smell-it is wonderful. What would that be? Parfum de fleurs de citrouille (scent of pumpkin flowers)!! If I know I’m pollinating, I will get up early. Generally between 6-8 am is when I pollinate them but I have forgotten sometimes and ran out at 10 am to pollinate.

Then after pollination be sure to close up the female with a twistie tie or piece of string for 24 hours as shown here. After 24 hours, you can let the flower open up cause it will either be successful or not and you won’t know till after at least day 10 (that is the benchmark) if it was successful. The female flower shrivels up and drops off (like an umbilical cord) and the baby pumpkin will get larger and larger. If the pollination didn’t take it could be because of several reasons. One reason is because it was too hot the day of pollination (over 90°F). This might cause some pumpkins to abort later. The second reason is because we didn’t get enough pollen on the stigma part of the female blossom. Either way, you’ll see the pumpkin start to grow and then suddenly stop. It looses it shininess, getting duller and softer and usually spots show up as it decays which is a self abortion.  If this happens, cut it off. That is why we pollinate more than we need because sometimes the plant self aborts its babies if something is wrong-kind of like a miscarriage for us.

14 comments on “How to tell when to pollinate a female giant pumpkin blossom

  1. mac says:

    Jannine,

    Thanks for the tutorial, it’s very clear now.

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  2. Emily says:

    Is the rule generally the same for growing mini pumpkins? (Jack-b-little & casperita) Sicne I’m not looking for large pumpkins, can I keep more on the vine than 2 per? Thank you! 🙂

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    • Yes! If I was growing regular or small pumpkins, I would keep as many as it produced. And you don’t have to hand pollinate them either-let the bees do that. That post is for giant pumpkin growers who want the biggest and heaviest pumpkin so they take off all but the biggest and they hand pollinate as they want to know who the parent plants are.

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  3. Nancy says:

    Can I hand pollinate with the males before they bloom?

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    • No you need to wait till they open and a female blossom opens at the same time in early morning. Take the male blossom off and peel off the petals so the only thing left is the pistol with the pollen all over it. Then brush it on an opened female flower around the interior of the stigma.

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  4. Bryan says:

    When I peal back the petals on the male I don’t see any yellow pollen . It seems to moist .no powdery pollen . Is it supposed to look like that..

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    • The bees get up really early in the am and take the pollen on a male flower that just opens up so by the time you get to it, the pollen’s gone. Look at the next male flower that looks like it will open up the next day and tie a string around it so it can’t open. Then when you get up, take off the string and peel back the flower petals and take the pistol which should be loaded with pollen and paint it on the female flower stamen all over. I’ve tried getting up at first light and the bees have been there first so this works well. You should pollinate the female flower first thing in the morning between 6-10 am.

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  5. Deby Glenn says:

    I’m loving your site? I leave for work at 5:30 am. I get lunch at 11:30- I’ve missed 2 pollination’s. Today I was home by 11:00 am there was still a female opened up. This plant is from seeds in a plastic bag. The plastic bag was marked on one side of bag labeled Cinderella. On the other side of the bag it was labeled Atlantic Giant. I never noticed it until after I had it home. I do have one other plant that was labeled Atlantic Giant… that was in a 4 inch pot from a nursery.
    I’m almost certain the plant with open female flower is a Cinderella or even a little b jack.
    Most of the pollen was off the the pistol’s still open….I noticed the female Stamen and flower tips was kinda… well…wet yikes. I still took the leftovers and added to the female. (I also Took a male from Atlantic giant n added then dropped 4 Pistons in the flower and closed it up.)
    Not sure about cross….(I’m a grown farm girl so) I’ll say cross breeding/pollinating. This shouldn’t be awkward to type sorry.
    My question is,
    1. Because the female flower was wet/gooey I wonder if that is a sign of some sort?
    2. do Atlantic and Cinderella or Little B jack cross?
    Thanks. I did put umbrella over the flower that is sealed up with my hair tie and also set 2 frozen Ice chest blocks on Styrofoam next to the Hopefully pollinated flower.

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    • Sounds like your not sure what’s in the bag marked cinderella and giant pumpkin so I wouldn’t bother trying to hand pollinate, just let the bee do the work. If you go ahead and actually buy some giant pumpkin seeds, then it may be fun to cross-pollinate them to see what you would get the next year.

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  6. Deby Glenn says:

    curious…If you look at the next male flower that looks like it will open up the next day and tied it closed. then the next am when you have that male flower all opened up. will you reopen the female from the day before? Or is your thought you will have a new female each day? I’ve never had a new female everyday yet. Thanks

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    • You must get a female and male flower that will open on the same morning to pollinate. Pollinating a Cinderella will still be a cinderella pumpkin but will have some giant pumpkin genes in the seeds. It will not affect this year’s pumpkins only the next year if you decide to grow it out. If you cross a female giant pumpkin and it is the one with the female flower, it will still turn out big but it will have the cinderella genes in it for the following year as well. I look at the blossoms and when they start to turn a slight yellow green, then they will open the next day and I’ve been putting a ziplock bag over both to keep the bees out so they don’t take all the pollen from the males or other pollen to the female. You can pollinate with more than one male flower if necessary. Just think if it as using a paint brush over and around the female inner parts to brush the pollen around her. If you don’t care then just let the bees do the pollinating. AS far as wet inside, not sure what that is about unless water got into it. I only cross giant pumpkins with giant pumpkins, not other varieties.

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    • They must be ready the same day as in the previous reply.

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  7. I have a mystery plant this year and this isnt it. good stuff tho

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