Meet the deceptively pretty creeping bellflower, and the gardeners ...

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It started as a few heart-shaped leaves, as it always does. Then they began to multiply. It was only when a few stems appeared, each studded with pretty drooping purple flowers, that Susan Forint decided to investigate. She took a photo of the plant in her mother’s Toronto garden, which is home to hundred-year-old peonies and other historical perennials, and did a reverse image search online.

“Ignorance was bliss,” said Ms. Forint.

The intruder was creeping bellflower, an invasive weed that’s known to overtake unsuspecting gardens and front lawns, choking out any other plants in the vicinity. They can be pulled out with only a pinch, suggesting they will be easy enemies to vanquish. But beneath the surface is a robust and resilient root system. Even the tiniest root fragment can sprout a new plant, giving it the nickname “the zombie weed.” It’s immune to most herbicides, can grow in any light conditions and survive long periods of drought.

Native to central and southern Europe, the creeping bellflower thrives in many urban environments in Canada. It’s so prolific in some cities, such as Toronto, Calgary and Saskatoon, many people assume it’s a wild, native plant.

“It’s one of my most-hated plants,” says Jonathan Bennett, an associate professor at the University of Saskatchewan who researches ecology and the management of invasive species. (Dr. Bennett has a personal beef with the creeping bellflower too: It’s currently littering his lawn.) “It’s near impossible to keep out of gardens.”

Once you know to look for it, you start seeing it everywhere. Peeking through manicured hedges, nestled along fences in public parks, sprouting up next to bushy hydrangeas and hostas. Growing between the tiniest cracks of asphalt.

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Dr. Bennett says that invasive plants, which cost the Canadian economy billions every year, can dramatically affect our ecosystems too.

“From an ecological perspective, the loss of biodiversity is the number one problem with an invasive species,” says Dr. Bennett. “If a single species dominates, it changes how everything functions.”

When Ms. Forint learned that the plant multiplying exponentially in her mother’s gardens, which she tends to, was the dreaded creeping bellflower, she sprang into action. Over the past few years, she’s spent countless hours battling the weed, employing different tactics she’s discovered online: digging, pulling out any root fragments and replacing with new soil; layering sheets of newspaper, compost and mulch. “The plant just reaches out to the margins to where you’ve laid down the paper,” said Ms. Forint. “I don’t know if we’ll ever get rid of it. But it’s starting to get a bit better.”

Ms. Forint has found camaraderie in Creeping Bellflower Battles, a lively Facebook group with more than 8,000 members from across Canada and the United States, who are equally obsessed with destroying the weed. In the group, which was started by a Minnesota man in 2018, bellflower-hunters share removal techniques, swap war stories and post photos of their victories: wheelbarrows full of the bellflower; dug up and mulched over lawns; the weed’s parsnip-like tuber roots, on display like a trophy hunter’s prize.

Michael Chu, an architect based in Calgary, has been waging a vendetta against the weed for some five years. After realizing he had a full-blown invasion, he excavated his entire front lawn, digging down 30 centimetres and tracing each root to its end, adding sheets of cardboard, weed barrier and 10 centimetres of mulch. He mostly has it under control now, but still relies on the herbicide Roundup to spot treat any leaf that pops up, like a pesky pimple that just won’t go away.

The creeping bellflower can reproduce by seed and its root systems, which can travel under fences, sidewalks and concrete barriers, meaning it can efficiently spread across neighbourhoods. Although its flowers are pollinated by insects, in the absence of pollinators, it can self-fertilize.

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This is why when he’s out in the neighbourhood, Mr. Chu warns neighbours if he notices the weed growing on their properties. He also can’t resist pulling out the long stems located in public areas, like along sidewalks and fence lines.

“My wife doesn’t like walking with me anymore because she’s like, ‘you just stop and start picking!’” said Mr. Chu.

Since most provinces don’t list the creeping bellflower as an officially regulated invasive species, many gardeners take a more grassroots approach to eradication. In Calgary, a man offered $5 for every bag of creeping bellflower someone brought him; in Toronto, a retired woman hands out informational pamphlets to houses she spots with the weed on their property. The Facebook group Creeping Bellflower Battles is full of discussions hashing out ways to speak to neighbours about the weed, many of whom just see it as an attractive plant that blooms all summer.

Dr. Bennett, from the University of Saskatchewan, notes how in Ontario, the prevalent invasive plant garlic mustard is suppressing tree seedling growth, which alters forest regeneration. And in the Prairies, the invasive cheatgrass is affecting wildfire cycles by creating fuel at the peak of the summer.

While creeping bellflower doesn’t typically grow in natural areas, Dr. Bennett says that could change. “Sometimes it just takes one little mutation, some key evolutionary change and they become more problematic,” he said.

For many gardeners, including Ms. Forint, the creeping bellflower has already reached the problematic stage. She grew up with the gardens in her childhood home, and they are worth preserving.

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That’s why for an hour or two every week, you’ll find her outside with her garden fork. She’s considered the sifting method – which involves using mesh to sieve the soil to catch the tiniest fragments of roots – but hasn’t gone down that road yet. This fall, she’s going to use some Roundup, which contains the herbicide glyphosate. “I’ve learned from the Facebook group that you either paint the leaves with a brush or with a bingo dabber,” says Ms. Forint. “They say do it in the fall because that’s the time of year when plants start bringing their strength into the roots.”

She’s not sure if this method will work, but it’s worth a shot. “I’m sure people will laugh at me. ‘She’s sitting there painting leaves,’” said Ms. Forint, imagining what her neighbours may think. “It could be very zen-like.”

1. When you first notice the flower’s heart-shaped leaves, pull them up and as much as the root as possible. Pulling out the weed prebloom can help prevent seed production.
2. Since it can also reproduce through its creeping root system, focus on digging up the weed’s white, fleshy rhizomes with a garden fork. Some gardeners swear by digging up to 15 inches of soil to reach the deepest roots.
3. Do not compost or dispose of the weed in yard waste bags. Instead, throw out the weed in black garbage bags so the roots do not regrow plants.
4. Although the weed is resistant to most herbicides, some gardeners swear by using Roundup to brush on the leaves.
5. If you’re planting wildflower seed mixes, double check that it does not contain Campanula rapunculoides.
6. Remain persistent in your battle against the creeping bellflower. It can take up to 10 years of regularly pulling out the weed as it appears to fully eradicate it.