Tuesday, May 14, 2013

Hand Pollinating Melons

At the beginning of each summer it often takes a while for Tucson’s wild (and domestic) bees to find the flowers in my garden. Often, during this time of year, I look around my yard wondering where the bees are hiding and conclude that if I want my vegetables pollinated then I will have to do it myself.

Male Melon Blossom - front view

Members of the Curbitaceae family (Cucumbers, Melons, and Squash) are monoecious. The Latin of this name means “one house” and refers to the separation of the reproductive parts of the plant into individual male and female flowers that grow on the same plant. The technique of hand-pollinating monoecious vegetables is pretty straight-forward. Here are some pictures to aid in hand pollinating melon vines.
Male Melon Blossom - side view

Before pollinating, it is important to ensure that both male and female flowers in bloom. Male flowers can be identified by the small short anthers with pollen in the middle of the flower and the thin stem, devoid of bulging, leading up to the flower. In contrast, female flowers exhibit a roundish folded stigma in the center of the flower and a thicker immature shape which contains the unpollinated fruit.
A Female Melon Blossom with immature fruit (Left)

Once the presence of a male and female flower have been verified, then comes the pollinating itself. With melon flowers I just pick the male flower, leaving as much stem as possible attached, and pull back the petals to expose the anthers.
Pulling back the petals of the Male Blossom to expose the anthers

Exposed Anthers of Male Blossom
To pollinate, I insert the male flower into the female flower just enough so that I can feel that the male anthers just make contact with the female stigma. One technique I found very effective to avoid damaging the female stigma is to gently rub the male anthers around in the female flower to release the pollen. After pollinating I then toss the male flower aside and hope for the best. If you desire to increase chances that pollination will occur you can either pollinate again with another male flower or you can wait until the next day to attempt the process again. This will help you to overcome male pollen that is not viable or a female flower that is not fully mature.
Pollinating Female Melon Blossom with male Anther

In general, both male and female flowers have a window of opportunity in which the bees (or people) can complete the pollination process due to the limited timespan of male pollen viability and female fruit receptivity. Male flowers lose their viability when the flower petals turn a pale color and close, while unpollinated female flowers are usually identified only after the fruit part of the stem turns yellow wilts. In order to encourage consistent flower production, I regularly remove any wilted fruit or pale flowers.
Female Melon blossoms progress (left to right): Immature, Pollinated, and Fruiting
Pollinating your plants may be necessary if you are growing in a greenhouse or if you need to isolate a specific vegetable variety (cultivar) from another cultivar that you are growing. If you are rouging or culling a specific variety for breeding purposes, it is important to pollinate your own plants by selfing. Rather than crossing plants using male and female flowers from different vines, selfing isolates qualities of a specific plant by only pollinating female flowers with male flowers of that specific plant. Once you have isolated the qualities of a vegetable variety and produced seed, you can then replant that seed to create a landrace (a large population of a variety that is adapted to your climate) by crossing as many plants of the new variety as possible. The purpose of a landrace is to keep future plants vigorous and strong by increasing genetic variability within a given population. Lack of cross pollination within a vegetable variety can weaken the variety and eventually lead to inbreeding depression.

So – why should a gardener hand-pollinate their melons if there are no natural pollinators? To watch as the female fruit grows.
A pollinated melon sets fruit and begins to grow. =)


  1. All sorts of fantastic information about veggie-growing in your blog. My main passion is growing veggies; but in NJ, nothing much is growing at the moment. The story of the bees in your blog, how your neighbor killed them all, brought tear to my eyes :-(. Honestly people have no idea about nature, climate change, bee collapse and all such important stories.

    1. Dear KL,
      Thank you so much for your comments. You are right to say that nature is important.

      Not only are bees needed for my vegetables, but they are important to keeping nature in balance.

  2. Thanks for this. I found out about hand-pollinating when my butternut squashes shrivelled after growing about 2 inches, but wasn't quite sure how to do it.

  3. Great tips Jay as I had not considered I may have to do it more than once...I do sometimes have to hand pollinate some squash.

    1. Thanks for the reply, Donna.

      Squash tends to blossom and set fruit (or not) all within one day but on some melon blossoms the petals will reopen for several days, during which time I have experienced a variation in fertility. Because of this variation, it is worth hand-pollinating again to increase my chances of fruit set before the blossoms close for good.

  4. You're a great teacher... I can always expect to learn something new from you. Thankfully we have plenty of bees here, several neighbors have backyard hives and we enjoy the fruits of their bee's labor. I must say that baby melon is as cute as a newborn should be.

    1. Thank you so much Carolyn!
      I like what you said about the melon. Perhaps that is why when my children were babies my inclination was to just "eat them up". (=

  5. Thank you so much for this post! It's the best explanation of difference between male and female melon flowers I've found. Thanks to you, yesterday I've found female flowers on my melon! Hope, there will be fruits.

    1. Thank you so much Olga.

      It really helps to have some pictures once in a while!

      I would really like to get back to this blog, but some health issues and my current location (renting a home with a shaded yard) keep me from gardening much.

  6. Hi Jay! This is such a great source of information about hand pollinating melon blossoms. I work for Garden Gate magazine and we would love to feature some of your photography in an upcoming issue, as we would like to help explain male/female melon flowers to our readers. I am not sure how to contact you, but please respond to this post if you are interested in sharing and being credited in our magazine.

    Thank you!
    Katie Meyer
    Senior Graphic Designer, Garden Gate Magazine

  7. Hi Jay,
    Thanks for sharing so detailed and valuable info. Certainly, I do crosses in Melons and Squash. Would you please share your experience on "how to identify the pollinated (by bees) and un-pollinated flower bud in Melon". It always difficult for me to choose the right flower for hand pollination.

    1. Pollinated flowers will "set" the fruit by continuing to grow in size. This indicates that the female flower was pollinated successfully.


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