Invasive species don’t just threaten biodiversity — they drain our economy as well, columnist notes
Editor’s note. This is the final instalment in a six-part series about invasive plants.Click on the following links for Part 1: Gardeners unknowingly fuelling invasive plant crisis, Part 2: The plants we love but shouldn’t trust, Part 3: Why invasive plants are everyone’s problem, and Part 4: GARDEN PATH: Silent swish of invasion: When ornamental grasses go rogue.Part 5: Invasive groundcovers: When ‘low-maintenance’ becomes ecological mayhem.
At every garden centre, there’s an invisible fork in the road — one aisle feeds only our eyes, the other feeds diversity.
Over the past five weeks, we’ve met garden “helpers” that weren’t so helpful — plants that promised beauty and convenience but delivered monocultures and maintenance headaches. We’ve covered climbers that strangle trees, shrubs that leap fences, grasses that form impenetrable walls, and groundcovers that behave more like carpet bombs than plants.
So as we close this series, it’s time to ask: Why do invasives spread so fast — and why our natives can’t keep up?
People often ask: “What’s the big deal? Aren’t new species just part of evolution? If a plant grows well here, maybe it’s meant to be here.”
The key issue isn’t that new species are arriving — it’s how fast they’re arriving.
For thousands of years, new plants slowly found their way into ecosystems through wind, water or gradual migration. Today, global trade has accelerated that process by thousands of times.
Every crate, nursery pot, ship ballast tank and transported soil load creates a pathway for species to move across continents — faster than ecosystems can adapt.
Are invasive species “superior”?
No. Most invasive plants aren’t inherently stronger or more “fit.” They simply arrive at the right time, in the right place, carrying the right traits — and with few natural enemies to stop them.
When a plant crosses oceans, it often leaves behind the insects, grazers, and diseases that once kept it in balance. Freed from those natural controls, it can grow and spread unchecked — outcompeting native plants still coping with hungry deer, caterpillars, moulds and mildews.
But that’s only part of the story. Many invaders come with stacked advantages — fast growth, abundant seeds or spreading roots, and the ability to thrive in almost any soil or weather. Add to that our habit of clearing land and moving soil — and you’ve created the perfect launchpad.
So when an invasive plant takes over, it isn’t because it’s “better.” It’s because it arrived faster than the rest of nature can adjust — in a world where relationships built over millennia are being rewritten in a single season.
The hidden cost of invasives
Invasive species don’t just threaten biodiversity — they drain our economy, too.
In Ontario alone, municipalities and conservation authorities spend an estimated $50.8 million each year managing invasive species and the costs ripple nationwide through lost crops, damaged forests, declining property values and flooded ecosystems.
Prevention is far cheaper than cleanup.
To learn more about the economic impacts of invasive species, click here.
While regulation is catching up, much of the responsibility still falls on us, the gardeners.
Before adding a new plant to your garden, take one quick step. Type the botanical name + “invasive” into a search engine. This simple check often reveals government fact sheets or risk assessments warning if a plant is invasive in your region.
But here’s the truth we’ve uncovered along the way: Invasive plants are strong. It’s that we’ve forgotten how strong native plants can be.
Every time we pull an invasive, the real work begins with the next question: “Who gets to grow here instead?”
Fill that opening with native groundcovers, sedges, ferns, or wildflowers — plants that hold the soil, feed wildlife, and keep the invaders from returning.
Not every plant in your garden has to be native. Research by Desirée L. Narango, working with Doug Tallamy, found that to support a breeding population of chickadees — a stand-in for broader food web health — about 70% of a landscape’s trees and shrubs needs to be native. That leaves 30% wiggle room for well-behaved non-natives — your lilacs, peonies, tulips, roses, hydrangeas, even a cherished hosta or two and many others.
The phrase “native plant garden” often brings to mind spring woodlands of trilliums and violets, or summer meadows alive with goldenrods, asters and butterflies. But native gardens don’t have to fit one mould. They can be diverse, eclectic, even refined — from cottage-style abundance to modern minimalism.
A formal garden border designed with native perennials. Photo courtesy of Mt. Cuba Centre/A Way to Garden
Be sure to check the publication, Your Guide to Native Ontario Plants.
The community ripple effect can mean transforming a your own yard can be contagious.
When one household replaces invasives with natives, neighbours notice. Swap divisions with friends, coordinate street-by-street native strips and suddenly you’re stitching habitat across property lines.
How to take action at any scale
Start small and move up when you’re ready. If you do nothing else… Just stop planting invasives.
Got 10 minutes? Snip the flowers/seeds off your invasive. Prevent spreading.
Got a weekend? Dig or smother one patch.
Planting something new? Choose a native equivalent.
Every patch we reclaim, every native we plant, is one small act of repair — for the planet and for the children who will walk it after us.
And together, those small acts add up to something powerful: a comeback for biodiversity, and for the gardens that nurture it.
A letter to today’s gardeners from the kids who will inherit your yards.
Dear Grown-Ups,
We love visiting your gardens — running barefoot through the grass, chasing butterflies, picking berries and pretending the trees are castles.
But please, leave us more than lawn — and less of what harms the land.
Before we were born, many people didn’t realize that so many beloved garden plants could be invasive — that beneath their blooms, they were quietly starving nature.
We miss seeing the many wonders — the dragonflies, the caterpillars, the butterflies — a garden alive with life. So please, plant things we can taste, touch, smell and discover.
Let lavender, mountain mint and hyssop brush our legs as we pass.
Plant pin cherry and serviceberry for the birds and for us — sweet fruit to share in summer’s sun.
Mix tall and short, spiky and soft — sunflowers, liatris, ferns and native grasses.
You don’t have to change everything.
Just make one wild corner.
One secret hideout.
One patch of real nature.
And when we’re older, we promise —we’ll keep planting where you left off — The Children of Tomorrow’s Gardens.
Photo credit: Ourdaysoutside
With gratitude to Cathy Kavassalis and Claudette Sims of the Canadian Coalition for Invasive Plant Regulation, whose insight and advocacy helped inspire these columns. The more I learn from their work, the more I realize how much more there is to learn.
Monika Rekola is a certified landscape designer and horticulturist, passionate about gardening, sustainable living and the great outdoors. Contact her at [email protected].
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