Garden expert advises ethical gardeners to 'first do no harm' in connection with invasive species

An invasive species educator in Sault Ste Marie, Ont., says gardeners may be unwittingly spreading invasive species by purchasing them in their local garden centres and taking them home, where they run out of control.

Abby Obenchain is a retired science communications specialist for the Ministry of Natural Resources and now volunteers with her local environmental group, Clean North in Sault Ste Marie.

She says she's been gardening for more than 50 years. But she still finds it shocking that plant nurseries and greenhouses promote plants to the home gardener that may end up wreaking havoc on the natural environment in Ontario.

"From an ethical standpoint as a gardener, I believe that it's imperative that the first rule of gardening is to do no harm," she said. "And so if we're having any impact at all on the ecosystem with our gardening, then we're not, honestly, we're not being ethical gardeners."

Obenchain says there are still many garden plants that can be purchased that also have the potential of a risk to health and even economic harm for municipalities and farmers who have to spend money to manage them.

"Unfortunately, here in Canada, we regulate way fewer garden species than the U.S. does," she said. "We're kind of behind the eight ball when it comes to this"

She points to plants with familiar names such as deadnettle, lily-of-the-valley and especially periwinkle, also known as vinca.

The vigorous ground cover has escaped the backyards of property owners along natural areas in Sault Ste. Marie, she says, and it's spreading and throttling native species such as trout lilies and trilliums.

Also, Obenchain says, plants can suppress young trees, so as the old trees die off, the area becomes a monoculture and ecologically dead.

Removing invasive species from your garden can be especially challenging, says Obenchain, and some species spread when the roots are broken and disturbed.

She cites Japanese knotweed as an example.

"Trying to dig it out actually makes things worse because it can cause the plant to launch exponential lateral root growth." 

While it is now illegal to sell knotweed in Ontario, it's also hard to get the herbicide that is the only effective tool in eradicating it.

She says if you do try to dig up invasives such as deadnettle and periwinkle, be sure not to compost them as that spreads them to landfills, and she says never dump yard waste in natural areas for fear of spreading non-native plants to wild areas.

Obenchain recommends gardeners join support groups online if they have an invasive to get advice on how to control them.

Demand for native plants increasing

Fortunately, she says, plant sellers are catching on to the idea of also offering native plants for sale which she says should provide more food for pollinators specific to Ontario.

That's probably due to increased demand, which is what the general manager of Southview Greenhouses in Sudbury has found.

Martha Reid says they changed suppliers this year to one which can provide native perennials such as trilliums, Canadian ginger and purple coneflower.

"One problem is with the natives, they're next to our regular perennials and they're not as showy, and some people do go for the colour but the more we have it here and promote it that people will become more knowledgeable with it," says Reid.