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. =)