Hand-Pollinating Zucchini

It’s time to learn about sex. Oh, you think you already know all about that? OK, but how much do you know about making baby zucchinis?

Perhaps your zucchini (or other squash) plants are producing plenty of flowers, but no squash. Or, maybe they start to grow little squashes but then the babies turn yellow to brown, get all wrinkled, and fall off. What’s wrong? It’s highly likely the problem involves zucchini sex.

All squash plants (and related crops such as cucumbers) produce two kinds of flowers, male and female. Here’s how to tell them apart:

zucchini-blossom-male-femalecsu-23jul04-lah-033s

The male flower has a long stem, while the female flower has a tiny squash at its base, and a shorter stem.

In order to produce fruit (to a botanist, squashes and cucumbers are really fruit), pollen from the male flower must be transferred to the female flower. Normally, bees do this sort of thing. However, bees haven’t been doing so well lately. There’s a mysterious disease ravaging the hives, and population numbers are down. Also, if the weather is extra rainy, or your plants are under plastic or polyester row covers—or if you’ve sprayed a broad-spectrum insecticide—bees may not be up to doing their job. Pollination is either incomplete, or not happening at all. In this case, it’s up to you.

Zucchini plants only produce male flowers to start with. If you don’t see fruit setting after those first blooms, that’s normal. But once you can identify female flowers, you should start getting squash. If not, here’s what to do.

Make sure you have both male and female flowers available. They should be newly-opened, not at all fading or wilted; early morning is best. Pick a male flower and carefully remove all the petals. That little structure inside is the stamen. The tip (called the anther) contains pollen. (Most kinds of flowers have more than one stamen, but in squash they’re all fused into one lump.)

zucchini-blossom-csu-lah-053Now look at the female flowers, shown at left (also notice the developing zucchini with a flower still attached to the end). They have little squiggly bumps inside the petals. Those are stigmas. Your goal is to transfer pollen from the male stamen to the female stigmas. You can use a cotton swab or paintbrush, but it’s easier to just dust the anther over the tips of the stigmas. Stigmas are somewhat sticky, and the pollen will adhere. One male flower can pollinate two or three female flowers.

There, you’ve done it. That wasn’t too hard, was it? Next, you’ll be looking for some unsuspecting neighbors to inundate with extra zucchini!

23 thoughts on “Hand-Pollinating Zucchini”

  1. Thanks so much for the complete description of hand pollinating zucchini. I just can’t depend on bees this year. I’ll have to check out your other posts. Susan

  2. Well, I just the dirty deed with the male and female flowers! I covered the female blossom with my garden glove because I thought something was eating them! I will remove in the morning and hope I see some babies! Thanks for the info- nuevo farmer!

      1. I hand pollinated my squash and bloody’wll knocked the female off the stem..no fruit therefore not so..any way to rectify situation?

    1. Good question. That really does sound like a pollination issue, but if you hand pollinated then it can’t be that. Or… maybe the pollen was too old, or not yet sufficiently developed? Maybe the female flower wasn’t quite ready? That’s all I can think of. I suggest asking someone local and/or someone who knows more about squash than I learned in my master gardening classes. I’m guessing your conditions are very different from mine here in Colorado.

  3. I have had a lot of success hand pollinating my zucchini and yellow squash. Sometimes I have to use a male flower from one plant to pollinate both pants. My big issue I have been having is that some days I have a bunch of female flowers blooming and no male flowers. Then the next day I have male flowers but the female flowers have all closed. Is there any way to harvest pollen to use in this case?

    1. Wow, that’s a great question. I have no idea! You could try picking the male flower and keeping it in a sealed plastic bag overnight. In fact, try two–one in the fridge, and one on the counter. But I don’t know if the pollen would still be viable. If you try it, please let me know. Now I’m curious!

      1. I am having the same issue. I picked 2 male flowers because there was no females this morning. I watered the zucchini this evening and found one female is really to open up tomorrow morning but there is no male flower to be open. I think I have to use the 2 males flowers I just picked. I don’t want to see the baby zucchini die again. The first 5 babies turned yellow and fell off because I didn’t know that I have to hand pollinate 😦

  4. I have a lack of mail flowers on my plants. Anyone know how to stimulate more male flowers from the plant?

    1. Usually the male flowers appear first. It’s very unusual not to have any, unless you’re growing a cultivar that’s specifically bred to only have female flowers. Many cucumber varieties are like this. Unless they produce fruit without pollination (some cultivars do), a few seeds of a pollinator cultivar is usually included in the seed packet.

  5. L a h I love this post I love the pictures too thank you so much I’m going to try today. I had a bunch of baby zucchinis growing and then they just all closed up and started to shrivel and now I read your post and I was sad because they were all dead. But now I’m looking again there’s another new yellow flower yay 😉

  6. Also, last week when I looked there was baby black ants all over them. I figured that’s why they were dying so I sprayed them with ant spray for vegetables. thought I killed them

  7. Ants won’t bother the squash plants, although they can “herd” aphids, protecting them from predators and eating the honeydew they produce. Have you tried hand pollinating the flowers? Usually, if baby squash don’t develop, it’s because pollen isn’t getting to the female flowers.

  8. my question….if the female flower blooms the day before it is still viable with a male flower opening the next day?
    the female flower will be closed but if you open it with your hand and use a fresh male flower I wonder if it would pollinate

    1. Good question! I’m guessing yes, but I’m really not sure. I hand pollinated my zucchini yesterday, as it’s currently living under hail cloth (thankfully, in light of last night’s storm), which also excludes bees. I guess we’ll find out. And if you try, could you please let me know whether or not it worked? Thanks!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s