Pollination in the Garden: Bees, Buzz, and Wind

A native bee inside a male squash flower

We've all heard the phrase "save the bees," but for many of us the relationships between plants and pollinators remain mostly mysterious. Luckily, we can learn a lot about pollination by making observations in our gardens and backyards. This blog will give you the buzz on how some common vegetables in your garden are pollinated (spoiler alert! they're actually fruits!). 

Nearly all of the world's flowering plants require pollination to reproduce. The ways in which these plants are pollinated differs, mainly due to the characteristics of their flowers (shape, color, reward type, patch size, etc). Some plants rely on wind or water to transfer their pollen, while the majority rely on insect pollinators (bees, wasps, flies, butterflies, beetles, ants, etc) and sometimes other animals (bats, birds, geckos, ect.) The most effective and efficient pollinators in our gardens are native bees and not the well known honey bee, which is a non-native species from Europe. While some plants are capable of pollinating themselves or using the wind, in the United States, we grow over 100 different crop varieties that either directly rely on or benefit from pollinators.

What is pollination and why is it important?

Pollination is the transfer of pollen from a plant's male to female parts. Typically, interactions between plants and pollinators are mutualistic, which means both partners benefit. Plants need to reproduce, but don't have legs to move around and pollinate each other, so animal pollinators help them out. Pollinators visit plants for food (pollen and nectar) and on their way to get it accidentally rub up on plants reproductive parts and spread around pollen. When male pollen from one plant reaches the female part of the same plant species, that plant is pollinated. 

Pollen is required to fertilize an ovary, which then forms a fruit. Fruits serve as the protective and often delicious vessel that a plant uses to get its seeds out into the world. According to the Xerces society,  fruits and seeds produced from insect pollination are "a major part of the diet of approximately 25% of all birds, and of mammals ranging from red-backed voles to grizzly bears."

Insect pollination: Cucurbit family

Watch out with your watering! This wet female squash flower is not going to get pollinated until it dries out!

The Cucubitaceae family includes cucumbers, melons, zucchini, squash and pumpkins. These fruits are notorious for either producing like crazy, or giving gardeners a lot of trouble. The reason these plants can be difficult is because they require insect pollination to make fruit. Each plant has separate female and male flowers. Male flowers typically bloom about a week before females to attract insects. Native bumble bees and squash bees are the most effective pollinators for this family, because they have co-evolved with these plants and have very fuzzy bodies that catch a lot of pollen. Squash bees nest at the base of squash plants at soil depths from 5-10 inches-- a good reason to not till your garden! If you are having trouble with the pollination of your Cucurbits, you should follow these steps to attract and protect pollinators. You can also try out hand pollinating- see this blog on incomplete pollination in summer squash. 

Buzz pollination: Nightshade family

A pepper flower

A tomato flower

Fruits in the Nightshade or Solanaceae family include tomatoes, peppers and eggplants. These plants all produce flowers that have stamens (male parts) completely encapsulating the stigma (female parts). This means that when an individual flower is vibrated by wind or a pollinator the stamens release pollen that falls down and fertilizes the stigmas. Although these plants are usually self-fertile, many different crops have shown to grow bigger and better fruits when pollinated by bumble bees or other native bees. In order for these flowers to release pollen, they must be vibrated at a specific frequency. Check out this video explaining this exciting phenomenon called "buzz pollination." You can also go visit a neighborhood tomato plant flower and watch it happen in real life!

Wind pollination: Corn

Many of the world's staple food crops are pollinated by the wind. This list includes rice, rye, barley, oats, and corn. Because wind is not precise, wind pollinated crops have to crank out a ton of pollen to increase their chances of pollination success. One corn plant alone can produce up to 2 to 5 million pollen grains! Every corn plant has both female and male flowers. The male flowers are the tassels, and the female flowers are the potential kernels (ovules) which each have a silk (functional stigma) attached that is covered in tiny hairs that capture the pollen. Each silk must be pollinated for each kernel of corn (seed) to develop. Wow! That really gives me a new appreciation for a cob of corn! Because of this pollination strategy, corn does best in larger patches of at least three or more rows.

Each silk has to capture a grain of pollen in order to to fertilize and develop each individual corn kernel.

Look closely to see a honey bee collecting pollen from these male corn flowers that together form a tassel. This honey bee will not help the corn reproduce, because the bee has no reason to visit the silks (female flowers) that are about three feet lower down on the corn stalks.

Any part of a plant that requires pollination to form is a fruit- so put on your botanical glasses and start looking at those zucchini, cucumbers, squash, tomatoes and peppers through a different lens!

Hoidal, A. N. (n.d.). Flower and fruit set in cucurbits. UMN Extension. Retrieved August 19, 2022, from https://extension.umn.edu/growing-guides/vining-vegetable-growing-guide 

Licht, M. (n.d.). The birds and bees of corn pollination. Iowa State University, Extension and Outreach. Retrieved August 19, 2022, from https://crops.extension.iastate.edu/blog/mark-licht-zachary-clemens/birds-and-bees-corn-pollination 

U. J. M. Shanika R. Jayasinghe, T. H. Saumya E. Silva, W. A. Inoka P. Karunaratne, "Buzzing Wild Bee Visits Enhance Seed Set in Eggplant, Solanum melongena", Psyche: A Journal of Entomology, vol. 2017, Article ID 4624062, 7 pages, 2017. https://doi.org/10.1155/2017/4624062

Friends of Edgewood. (n.d.). Nightshade family. Retrieved August 19, 2022, from https://friendsofedgewood.org/nightshade-family 

Xerces society. (n.d.). Native bee pollination of Cherry tomatoes. Retrieved August 19, 2022, from https://xerces.org/sites/default/files/2018-05/12-044_01_XercesSoc_NativeBeePollination_Cherry-Tomatoes_web.pdf