WHAT'S AN INVASIVE PLANT?

Invasive plants can be pretty. They may be sold in garden stores. They may be familiar faces in your own garden. But when they escape to the wild, they can cause havoc.

Q: What’s an invasive plant?

• Invasive plants are plant species that are not native to our region. They tend to grow rapidly, spread quickly and widely (through fruits, seeds or roots) and can grow just about anywhere. Because these species did not evolve here, we don’t have the controls (insects, viruses, fungi, rusts) that keep them in check in their own part of the world. You might think of them as “superweeds”.

Q: Why are invasive plants a problem?

• They outcompete and displace native plants that wildlife depend on.
• They can alter water flow and lead to erosion and/or less available water.
• Some create and increased fire hazard.
• Some contain substances that are toxic to people and animals.

Q: How do invasive plants spread?

• Improper disposal of garden waste
Although it might seem like a good idea to “recycle” your garden debris into a natural area, what you’re really doing is introducing plants that can smother, choke and otherwise ruin parks, greenways and other greenspace needed by wildlife – and enjoyed by people.

• Unintentional dispersal (by direct growth)
Many invasive plants are rapid-growing and fast-spreading. English ivy, for example, can spread up to 4.5 metres in a single year.

• Unintentional dispersal (by seed)
Many invasive plants are prolific seed producers. One purple loosestrife plant, for example, can produce 3 million seeds! These can then be dispersed by water, people, animals, vehicles, etc. to new areas.

• Intentional introduction as garden ornamental
Many invasive plants got their start in someone’s garden. Most were exotics brought from other parts of the world. But here, they don’t have the same natural predators or checks to keep them under control and they literally go wild.

Q: Why do people buy invasive plants?

• Invasive plants can be pretty, but the problems they cause are not
Yellow flag is admired for its big blooms; periwinkle is a pretty ground cover and holly is a Christmas favourite. But each wreaks havoc in our parks and other natural areas by displacing native plant species needed by wildlife and/or by altering water flow, stealing nutrients and sunlight.

• Invasive plants can be easy to grow and can grow quickly – but that’s also what makes them invasive
Sometimes, homeowners looking for a quick solution to a bare spot will choose a plant lauded as a “fast spreader” or a “vigorous self-seeder”. Unfortunately, invasive plants tend to spread or seed themselves right out of your garden and into the parks and natural spaces nearby.

• Invasive plants can be readily available – but so are more appropriate alternatives
Many garden centres, supermarkets and corner stores continue to sell invasive species such as English ivy, English holly and lamium. But just because something is being sold doesn’t mean it’s a wise choice. Discriminating consumers who choose non-invasive alternatives can help change what’s for sale.