Getting rid of the invasive plants in our gardens — even the ones we love

Burning bush is an ornamental shrub introduced from China into North America in the mid-1800s. It is planted mainly for the bright red foliage it develops in the fall. A single specimen (planted in a sunny spot to get the brightest red foliage) can be spectacular. The most entertaining thing about it is that its common name in large parts of the U.S. is winged wahoo. Even saying “wahoo” is fun; saying “winged wahoo” takes it to a different level.

But this week, my winged wahoo came out. Dug out, roots and all. Left to dry and then put into my yard waste container. (I had unthinkingly offered it to a fellow gardener in my neighbourhood, but realized later that made no sense at all given the reason I was evicting it from my garden.) Making the execution easier, I have a Japanese maple — a garden “volunteer” I was kindly given two years ago — that will give me the same great red colour in the same spot.

Burning bush is an invasive plant and, along with a fairly long list of other “common” garden plants, poses a serious risk to the wide range of other plants, native and introduced, that make up what we call biodiversity. It spreads rapidly, chokes out other plants and is inedible to wildlife such as deer. Minnesota and Wisconsin, among other jurisdictions, have made the sale of it illegal. In part of the northeast U.S. (much the same climate as ours), burning bush carpets valleys, roadside ditches, forests, pastures and meadows.

I live not far from Churchill Park in Westdale, which merges almost seamlessly into the Princess Point and Cootes Paradise South Shore. My burning bush — along with others — is a threat to the fabulous natural areas there and the hugely diverse range of trees, shrubs and other plants that populate them. But enough about my garden (for the time being).

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• Dec 31, 1969
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• Dec 31, 1969
• Comments

Gardeners are going to be hearing a lot more about invasive plants and their dangers this year and in the coming years. The Ontario Invasive Plant Council has been working vigorously to get gardeners and garden centres on board and reduce the sale and use of invasive plants in gardens.

Cathy Kavassalis, a co-founder of the Canadian Coalition for Invasive Plant Regulation, is using her considerable talents to get the word out. She’s also a member of Halton Master Gardeners and a frequent speaker to groups in southern Ontario. She knows what she’s talking about: She’s a passionate gardener, a former board member of the Royal Botanical Gardens and has a master’s degree in environmental education.

“Gardening is the largest pathway for the introduction of invasive plants,” she says. “Maintaining a garden free of invasive species not only reduces their spread, but also protects local biodiversity.”

Eliminating invasive plants does not mean using all native plants, she emphasizes. There are lots of useful “introduced” plants, not native to North America, such as apples, tomatoes and cucumbers, and ornamental plants such as peonies do not spread uncontrollably.

“These non-invasive plants coexist without outcompeting native species or causing substantial changes to existing ecosystems. Understanding the difference is crucial for selecting plants that enhance rather than threaten local biodiversity.”

Kavassalis has had her own revelation and turning point.

“My son sent me photo to identify a plant covering a large area along Sixteen Mile Creek (in Oakville). It was butterbur, (Petasites hybrida or P. japonica), a plant I had excitedly added to my own garden 20 years ago ... along with another highly invasive plant, the yellow flag iris. Despite my initial enthusiasm, I watched as both plants escaped beyond my garden, compelling me to jump fences in the neighbourhood to remove them apologizing to my neighbours as I went. Many visitors to my garden were impressed by the massive leaves of the butterbur and the bright golden flowers of the iris, and they too added these invasive species to their gardens, unknowingly contributing to their spread.”

Kavassalis says some garden centres are not stocking invasive species or posting information to customers about the threat. But other garden centres are responding to customer demand. She says most garden centres would welcome invasive-plant legislation because it would level the playing field. But crucial, she says, is informing gardeners about invasive plants and the threat they pose.

So, what are some of the familiar invasive plants found in home gardens? Well, aside from the burning bush, periwinkle is one of the most common. English ivy and goutweed are well-known for their aggressiveness in home gardens and they spread to the wild, too. Norway maples are just a weed in tree form — and will spread like wildfire in the right conditions. Garlic mustard is known for its ability to spread almost anywhere. (I was at Princess Point one morning this week and garlic mustard is already coming up fast, tall and thick.) Creeping Jenny and Japanese barberry are both considered highly invasive and are prohibited in parts of the U.S.

Lily-of-the-valley is an invasive plant and is crowding out other plants in wooded areas throughout this area. And, hate to say it, so is miscanthus — the tall ornamental grass that is also coming out of my garden. Tree-of-heaven is an ecological nightmare. It was introduced from China, is described as “aggressively invasive” and is also the host plant for spotted lanternfly, an extremely destructive insect that kills plants and ruins fruit crops.

Yellow flag iris is an invasive aquatic plant that creates great mats of underwater roots, crowding out other plants and actually impeding water flow. Each plant releases hundreds of floating seeds. It’s a noxious weed in British Columbia and a threat in waterways across the country.

There are several dozen other invasive species and you can get more information on them by searching for “invasive plants Ontario” in Google or another search engine. The Ontario Invasive Plant Council will be near the top of the results. You can also search for “Grow Me Instead Ontario.”