Invasive Plants of the United States and Canada

Since the arrival of European settlers, a phenomenal number of plants have been imported into Canada and the United States. Sometimes these were edible plants used in agriculture, for their supposed medicinal values or for their ornamental value alone. Others arrived inadvertently, sometimes hooked onto a boat. And we continue to introduce them, without really knowing whether they can escape from cultivation or, worse still, damage our ecosystems by taking the place of native plants. Even species recognized as invasive continue to be sold commercially or spread in our gardens, taking advantage of our ignorance.

To be fair, we can’t necessarily know whether a plant will be invasive before we try it, unless it spreads aggressively in its country of origin. What’s more, I’ve found that there is no universal register of invasive plants. Of course, every province and state in Canada and the United States has its own list of invasive exotic plants, but there is no centralized database easily accessible to the public. Not to mention that many plants are not yet officially labeled as invasive, although they are in other places, or have the potential to be.

And Why Is It So Important?

Many exotic plants have become naturalized here without damaging our ecosystems. They have become part of our landscape and are so common you’d think they were native. Others have had and continue to have major impacts on our natural habitats, farms, health and culture.

For a start, invasive species often crowd out native plants for resources such as food, water and habitat, which can lead to population declines and even extinction for some species, upsetting the natural balance of ecosystems. This leads to a loss of biodiversity, which is essential to the maintenance of these ecosystems. Reduced biodiversity can make habitats more vulnerable to environmental change and less resilient to disturbance.

Other Consequences of Invasive Exotic Plants

The presence of invasive species can even alter ecosystem processes and functions, such as nutrient cycling, water flow and fire regimes. These disturbances can have cascading effects on other species and ecosystem services, leading to further ecological disruption. This can go as far as altering soil chemistry or changing hydrological patterns.

Invasive alien plants also harm agriculture by competing with crops for resources and degrading soil quality. Controlling and managing these species is costly. Government agencies and private landowners often spend large sums of money to control invasive species.

We must not forget the effect some invasive species have on human health and safety, by producing toxins or provoking allergic reactions.

Some invasive plants can also have an impact on cultural resources and traditional practices, particularly for indigenous communities. They can disturb culturally important landscapes or threaten the availability of culturally important plants and animals.

So What Do We Do About It?

Gardeners can contribute to the fight against invasive plants by avoiding their use in gardens and removing them from their properties. Just be careful! Don’t compost these plants when you remove them! By using more native species, you can easily solve the problem. Make sure to buy your plants from a reputable retailer.

You can also inform yourself and others about different invasive plants, volunteer for removal projects and support local regulations to prevent the spread of invasive species.

To help you, I’ve compiled several lists of invasive exotic plants from Canada and the United States. These plants are not necessarily invasive where you live: conditions are not the same in California as they are in Nunavut! Some plants may even be native to your region, but not to the other end of the continent. There are even vegetable plants on the list that have the potential to escape cultivation, and houseplants too.

So take this list with a grain of salt: if a plant you own or wish to use is on the list, don’t panic! Check with your regional government or local environmental groups to find out if the plant is, or could be, invasive in your area.

In Quebec, the reference for invasive plants is the Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et. For more information on invasive alien plants in Canadian provinces, visit the Canadian Invasive Species Council website. In the United States, you can visit the National Invasive Species Information Center.

List of Invasive and Potentially Invasive Alien Plants for Canada and the United States

You can help by mentioning in the comments any plants missing from this list, or by pointing out errors. Over 1,500 species or varieties have been collected.

Once the list is complete and corrected thanks to your support, a note will be added to this website next to the name of each potentially invasive species. You’ll be able to check for your region before using any of these plants.