Summertime Science in the Garden: Pollination

Bumblebee visiting gayfeather flowers in my dad's garden in Maine

Summer is a great season to spend time in a garden, and you often receive a little science lesson in the process. I enjoy watching various pollinators at work as they visit flowers. One of my favorites is the bumblebee, which is able to access pollen unavailable to other pollinators. Its secret is buzzing at a specific frequency that causes the flower's anthers to open and release pollen. (To learn more about buzz pollination, see the link at the end of this post to a Science Friday video on this topic.)

I learned about the importance of pollinators the hard way one year when my zucchini plants produced lots of flowers but no zucchini! I discovered that zucchini and other squash flowers are monoecious, meaning they have separate male and female flowers on the same plant. They can't self-pollinate, like some perfect flowers do, but instead rely on pollinators for the flowers to develop into fruits, the zucchini. Pollinators carry pollen from the anthers of a male flower to the stigma of a female flower. You can see these flower parts in the photos below, taken in my plot in the Juniper-Front Community Garden in San Diego.

Male squash flower with pollen-covered anther in the center

Female flower with stigma in the center

Fellow gardeners suggested that I plant some flowers to attract pollinators, and this has been very helpful. I learned that humans can serve as pollinators, too! This is a fun activity to do with kids. To hand pollinate a zucchini or other squash flower, remove the petals from a male squash blossom, and rub its anthers on the stigma of a female flower. One male flower can be used to pollinate multiple female flowers. 

Female blossom- note ovary below petals

Three days later: ovary developing into fruit

Male flower- note absence of ovary below petals

Once the flower has been pollinated, the pollen forms a tube that travels from the stigma down through the style to fertilize the ovules at the base of the pistil, triggering the development of the zucchini fruit. I now use this trick to pollinate my zucchini and spaghetti squash flowers with great success! 

If you enjoy watching pollinators and think you might be interested in helping collect data on pollinators in your area, you can learn about a citizen science project called The Great Sunflower Project in this blog post:

Get Outdoors with Citizen Science! The Great Sunflower Project

To learn more about buzz pollination, check out this Science Friday video:

Science Friday Video on Buzz Pollination

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