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Hand Pollination of Squash and Zucchini (Cucurbits)

squashstunts.jpgWe have had quite a heat spell here in the Southeast and my summer squash and zucchini seem to be producing, but many seem stunted and/or fall off the vine (as illustrated in pic).  The plants are very healthy otherwise, and though there are many possible factors like excessive heat, the most likely suspect is the lack of the bee pollinators. It is now common knowledge that there is a huge decline in the honey bee population, and I have not really seen any around these cucurbits. Therefore, I am going to need to attempt hand pollination for the first time.

malesquashflowers.jpgThese cucurbits bear both male and female flowers and because the pollen is sticky, they must be pollinated by bees (as wind will not move the pollen around). The male flowers are pictured here on the left and they are borne on a long stalk. Many times pollination is unsuccessful because there can be an early preponderance of male flowers before the female flowers open.

femalesquashflower.jpgAs can be seen here, the female flowers are borne on a much shorter stem, and the presence of the ovary (future squash) can be clearly seen. An important note is that pollination must be performed early in the morning (by around 10:00) when the flowers are open. Later in the day, the petals close and fermentation ruins the process.

malestamen.jpgWhat I have done here is to snip off the petals from a male flower and thus expose the stamen’s pollen producing antlers. The next step will then be to rub this onto the female ‘stigma’ to ensure pollination. An alternative method is to take an artist’s paint brush and transfer pollen from the male to the female flower. However, I feel the above method is easier and probably less prone to failure.

handpollinatesquash.jpgThe last step is to now rub the male antlers onto the female stigma and this should complete the pollination process. It is common for male flowers to fall, but the test of successful pollination for the female flowers is for them to remain on the vine. It would therefore probably be a good idea to place a little band around the pollinated flowers so as to track the progress etc.

To be honest, this is a new process for me as I haven’t grown cucurbits for a couple of years – and did not have to previously deal with inadequate bee pollination. Therefore, my steps here are developed strickly from researching this hand pollination method, but I have no prior experience to draw on. This certainly seems like it might be a bit of trouble however, the sad part is that I am afraid we are now going to have to live in a world largely without bees (if that is possible!).  Here is a nice link illustrating squash flower anatomy. Please provide your comments if you have experience in this process.

4 Responses to “Hand Pollination of Squash and Zucchini (Cucurbits)”

  • Carol Lyn:

    Thanks so much for your website. I have been searching forever for some tips on my back yard garden. I am in NC so not to different from you weatherwise. I have zucchini plants that are SO pretty but producing nothing. They have had tons of flowers but I notice the flowers just drop off and no female ovaries seem to be developing. After reading this post, I went to look and on closer examination there is at least ONE female flower. I am going to attempt the pollination you suggested as I have not seen any bees around since the azaleas bloomed in April!

    Thanks for the tip any others will be totally appreciated, wish me luck! lol

  • Julia:

    I just tried to hand pollinate but the male blossoms were the only ones opened. The female were much less developed. Any suggestions?

  • admin:

    Julia, my own observation is that in the beginning of the season, the male blossoms were more numerous and opened/matured first. However, I think that the female flowers should probably mature and catch up soon (provided that they are disease free and getting adequate nutrients and water etc). What part of the country are you located?

  • Kristie:

    Thank you so much for your detailed pictures and instructions. I have been asking other gardeners why everything but my zuchinis and peppers are growing and they suggested the lack of bees. I will be trying this first thing tomorrow morning!

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