Beating back invasive plant species

Posted January 2006

By Joanne Day, Fisheries and Oceans Canada

Sometimes a plant from another ecosystem finds just what it needs in your area. As it flourishes and spreads, it can crowd out native plants. To humans, one green thing may seem as good as the next, but a caterpillar or chickadee may have food or habitat needs that only native plants can supply. Even insect pollination patterns can be affected. Before you know it, the local ecosystem is out of balance.

Streamkeepers know about this problem, as they work to protect or restore riparian habitat. They need to identify invasive species before they become too well established, and replace them with beneficial locals.

The best time of the year to remove invasive plants is from August to April. If you are weeding out a herbaceous species, try to do it before it flowers. (Some of us wonder why it is that so often the species that must be removed is prickly, like blackberry, or downright nasty, like that giant hogweed, which can raise a rash on your skin.) Hardy and opportunistic, alien plants are often difficult to completely remove. Your best strategy is to understand how the species propagates, and be ready to replant with native species right away. Invasives love fresh dirt and open space.

For particularly thorny problems, you can get help from experts on the UBC Botanical Garden’s online discussion forum.

Module 7 of the Streamkeepers Handbook contains a useful index of native species suitable for riparian re-vegetation projects. It will help you plan your project, prepare the site, and organize follow-up maintenance. You may be able to use cuttings or seeds, or you may need to buy or salvage plants. Check with your municipality to see if there is a development planned from which you can rescue native plants. The chickadees will thank you.

One of ours: a sword fern is salvaged from a development site by Mike Gosnell.


For resource information about species native to B.C. and plant identification, click here