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Pollinators in the Vegetable Garden

June 21 to 27 is National Pollinator Week

I am sure all of you have seen or read about the campaign to “Save the Bees,” but did you know that these campaigns don’t tell the whole story? Ontario has over 400 native species but the ubiquitous European honey bee we see in the ad campaigns is a non-native bee. Also, the campaign concentrates solely on bees, but wasps, bats, birds, flies, moths and other insects are also important pollinators with declining populations. 

An example of the Save the Bees Campaign

Food and Pollinators

Many studies state that approximately one-third of all the food you eat is available because of pollinators. Pollinated crops hold an economic value of $690 billion per year world-wide. This is big business! Everything from the world’s favourites like chocolate and coffee to apples requires the plants to be pollinated.

What about your home garden? 

While it is true that a lot of what most people grow in the garden doesn’t need to be pollinated, the plants that do need it won’t produce fruit at all without being pollinated. Almost all of what we traditionally call fruit needs to be pollinated, this includes raspberries, strawberries and blueberries. Vegetables like cucumbers, watermelons and pumpkins also need to be pollinated.

In fact, squash has evolved to be pollinated by two native solitary bees, the squash bees, Peponapis and Xenoglossa species. These squash bees are so specialized they only pollinate squash plants! The squash plant produces male and female flowers, but sequentially, not all at the same time. The male squash bee visits the flowers very early in the morning, looking for mates. He can often be found sleeping in the dying flower bud later in the afternoon. Meanwhile, the female squash bee forages in the flowers, as squash is their sole source of pollen. By the time a honey bee visits the flower, pollination is usually already complete, rendering the visit redundant. If the squash flower doesn’t get fertilized, the fruit is aborted by the plant and you don’t get any yummy zucchinis or pumpkins! 

A zucchini flower waiting to be pollinated
Vegetables that need pollinators: Vegetables that do better with pollinators: Vegetables that don’t need a pollinator:
Melons and watermelons Tomatoes All leafy greens
Berries Peppers Brassicas incl. broccoli, cauliflower, cabbage and kohlrabi
Tree fruits (i.e. Cherries, apples, pears etc) Eggplants Root veggies such as carrots, parsnips, salsify, potatoes, sweet potatoes, horseradish and ground level root veggies such as beets, turnips, rutabagas

Other Pollinators 

As previously mentioned, birds, moths, flies and beetles are also important pollinators. Many of these species have become very specialized, pollinating only one or two types of flowers. And, although not many studies have been done, it appears insects are also important crop pollinators. Insects may not carry as much pollen from flower to flower as bees do, but they have been observed visiting flowers more often than bees, meaning they may be doing just as much of the pollinating as bees. 

Butterflies and moths are also important insects, but remember that these creatures start out as caterpillars, and if you rid your garden of caterpillars, you rid the garden of beautiful butterflies and moths!

A black swallowtail caterpillar munching on carrot leaves. These caterpillars rarely do any serious damage to veggie plants, so leave them be.

Always be sure to identify your insects before considering pest control in the garden. Most insects in the garden are benign or helpful!

Even midge flies are needed as pollinators!

Gardeners Can Save the World! 

First, take the pledge to never use pesticides. Unless you have no choice, such as when a pest is so abundant you will lose your tree or other plant material, refrain from using toxic pesticides. Nature will balance itself out, so pests one year may not be an issue the following year, when their predators gain in number. If you must use pesticides, try the least harmful ones first, such as soap and water (40 parts water to one part soap, leave for 10 minutes then rinse with clear water). 

Second, plant lots of different plants to increase the biodiversity in your yard. One plant species won’t feed the hundreds of insects that are in our environment. Remember to use native plants whenever possible. Norway maples, for example, support 2 species, Burr Oaks, on the other hand, support over 500 species! 

Third, limit the use of outdoor lighting. I am sure you have all seen moths circling outdoor lights. Believe it or not, the drive to fly towards light is stronger than the urge to mate. Many of these moths, and insects like fireflies, end up dying from exhaustion or predation rather than reproducing to form the next generation. If you must use outdoor lighting, consider motion sensors or use bulbs that produce amber- or red-colored light, which produce wavelengths that are less attractive to insects. 

For more helpful tips on how to help pollinators see the box below. 

We all want our vegetable gardens to be successful. Part of that is learning to let go of perfection. What does it matter that your cabbage leaves have a few holes in them from caterpillars, when the caterpillars in turn feed a family of chickadees? We have to stop controlling the wild and learn to live with other species, even the bugs!

  Add flowers in and around the garden – annual, perennials – both can help!

  Do not be in a hurry to clean up your garden. Raking and leaf blowing before it is consistently 10C during the day (or until you    see a bee flying around), will destroy the homes of overwintering insects and bees. This will expose them to cold weather and    they will die. 

  Let some of your herbs and vegetables flower

  Leave grasses and other ‘dead’ stems over the winter. Cut back to the ground in the spring (when it warms up). 

  Leave a small portion of your garden bare – no mulch – for burying insects. 

  Do NOT till your soil! Many native bees nest underground.

References:

Beechey, L. 2019. Ontario Nature. Insects at Risk in Ontario. [Online]. https://ontarionature.org/news-release/insects-at-risk-in-ontario/

Borenstein, S. 2021. PhysOrg. Scientist Decry Death by 1,000 Cuts for World’s Insects. [Online]. https://phys.org/news/2021-01-scientists-decry-death-world-insects.html

Cane, J. US Department of Agriculture. Squash Bees. [Online]. https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/squash_bees.shtml

Government of Ontario. 2020. Species at Risk Ontario. [Online]. https://www.ontario.ca/page/species-risk-ontario#section-4

Jones, G. Horticulture. 2014. Vegetable Crops that Do Not Need Pollinators. [Online]. https://www.hortmag.com/edible-gardening/vegetable-crops-that-do-not-need-pollinators

Kawahara, A. 2021. PNAS. Opinion: Eight Simple Actions That Individuals Can Take to Save Insects from Global Declines. [Online]. https://www.pnas.org/content/118/2/e200254711

Macdonald, M. 2020. West Coast Seeds. Squash Pollination. [Online]. https://www.westcoastseeds.com/blogs/garden-wisdom/squash-pollination

Rader, P. 2016. PNAS. Non-Bee Insects Are Important Contributors to Global Crop Pollination. [Online]. https://www.pnas.org/content/113/1/146

Terpstra, J. 2017. Ontario Agricultural College. Meet Ontario’s Pollinators. [Online]. https://www.uoguelph.ca/oac/news/meet-ontarios-pollinators

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