Any avid gardener or plant enthusiast knows of invasive plant species in Ontario such as dog-strangling vine, Japanese knotweed, and phragmites. These are listed on the province’s Invasive Species Act, which prohibits—and in some cases restricts—the buying, selling, breeding, importing, or trading (among other regulations) of about eight different invasive plant species within the province.
But Canada is home to some 500 invasive plant species, 441 of which are in Ontario, and about 98 per cent are not regulated under the act. What’s more, some of these plants are still bought and sold regularly, likely by unknowing retailers and purchasers. That’s because the plants can sometimes look decorative. But looks can be deceiving.
“Everyone wants to have beautiful plants,” says David Dutkiewicz, Entomology Technician with the Invasive Species Centre. “The problem is that, if they’re invasive, once they get out they can become a nuisance.”
What is an invasive plant species in the first place? Any plant that has been introduced to an area that’s outside of their natural range, and whose spread can cause significant ecological, economic, societal, and environmental damage.
And the Canadian Council on Invasive Species advises the damage invasive plant species can cause is widespread. Not only can they overtake native species by exhausting resources like water, nutrients, and space, but they can also introduce new crop diseases and pests, and cause issues for human health as well. Take giant hogweed and wild parsnip for example. Both are invasive plants with sap that’s known to cause skin rashes.
Periwinkle, a purple-flowered groundcover, is considered highly invasive by Ontario Parks and Ontario’s Invasive Species Awareness Program. And yet, it’s still sold in some garden centres across the province to this day. Just last month, the Hamilton Conservation Authority advised folks to look in their gardens for periwinkle, along with English ivy, and goutweed—all invasive groundcovers—and remove them. The plant can outcompete native species and affect biodiversity.
“I know several people who have periwinkle in their gardens,” says Dutkiewicz, adding that the plant can sometimes be contained in gardens by grass edging and other methods. “Without a physical barrier in place, though, periwinkle can take over nearby forest floors.”
Another example is Himalayan balsam, a pink, orchid-looking plant that is also commonly distributed across Ontario and throughout Canada. It is known to overcome native plants that help reinforce riverbanks, thus contributing to soil erosion.
“It’s also a member of the touch-me-not group,” says Dutkiewicz. “Their seeds travel in water and on people, meaning they can spread much farther.”
For the concerned gardener, Dutkiewicz advises doing research about invasive plants before hitting the garden centre. “I always say take a walk through the greenhouse, see what you like first, and then go back and pick all your flowers.”
Gardeners might also consult the Ontario Invasive Plant Council’s most recent “Grow Me Instead Guide,” which lists invasive garden plants and then suggests similar native or non-invasive species to plant instead. For example, if you love the look of periwinkle, the guide suggests planting wild geranium instead.
Shoppers should also think twice about where they go to purchase their plants. Online ordering can be particularly challenging for procuring native species. Dutkiewicz points out that with online seed orders, you might not even get the seeds you asked for. Two good retailers he recommends are the Ontario Seed Company and Northern Wildflowers. As for in-store locations, Dutkiewicz says that smaller, family-run organizations tend to be a bit more wary about selling invasive species.
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