Alberta - Edmonton Horticultural SocietyThe Alberta Weed Control Act includes two lists of weeds: “prohibited noxious” and “noxious”. A list of the weeds on each list can be found HERE. These plants are invasive and/or have a significant negative ecological or economic impact in Alberta. Negative impacts include aggressive displacement of beneficial native vegetation, toxicity to agricultural animals or plants, damaging to river banks and waterways, hosts for diseases that attack agricultural plants, or parasitic.

Prohibited Noxious Designation

Noxious Weeds - bighead knapweed

Bighead Knapweed

“Prohibited noxious” weeds are considered nasty invaders and are illegal under the Alberta Weed Control Act. They must be eradicated if present in gardens, on farmland, or in any landscape in Alberta. Garden centres and nurseries must not sell these plants, nor should anyone bring them into the province as cuttings, plants, or seeds.

Noxious Designation

Noxious Weeds - creeping bellflower

Creeping Bellflower

“Noxious”  weeds are less nasty but do not purchase, plant, or transplant from other sites. Remove or control existing plantings. Local authorities may move plants from the “noxious” list to the “prohibited” category, so it is wise to check with your municipality.

Not all municipalities recognize all the plants on the lists as noxious. That does not mean they do not exist in that municipality. The law still applies. You can address questions and concerns to the Alberta Ag-Info Centre: 310-3276, or your local County or Municipal Agricultural Fieldman or Weed Inspector. Below are links to some local municipalities.

City of Edmonton Weed Control

St. Albert Weed Control

Strathcona County Weed Control

Parkland County Weed Control

There are also smartphone apps for weed identification. Edmonton residents can use the City’s 311 app to take a picture of an unknown or suspected weed and get an identification.

What Responsible Gardeners Should Do

Local gardeners know and love many of these plants. It will be hard for many of us to rid our gardens of these plants, but we must. What we grow in our gardens has an impact on the wider environment. The EHS encourages all gardeners to be good environmental stewards.

noxious weeds - Image by Keith Williamson - Article by Edmonton Horticultural Society

Himalayan balsam (c) Keith Williamson, licensed for reuse under a Creative Commons Licence

Before getting out the garden spade, however, take care to note the specific plants on the lists. Some of these plants have species or cultivars that are NOT on the list. Common barberry is prohibited, but barberry cultivars like ‘Rose Glow’ are not. Common names are also confusing: purple loosestrife (Lythrum salicaria) is prohibited, but Alexander loosestrife (of the Lysimachia genus) is not.

Do not share these plants with others, and that includes giving away seedlings, seeds, cuttings or plants. Please do not bring these plants to the EHS Perennial Exchange. Garden Competition entrants found to be growing a prohibited noxious or noxious weed will receive a 25 point penalty. The EHS will make every attempt to ensure that gardens on our annual tour do not contain these plants.

Articles in gardening magazines may encourage you to grow these plants. This may be because the magazine’s audience is broader than just Alberta, or the writer may be unfamiliar with the Alberta Weed Control Act. Check any unfamiliar plant suggestions against the list.

More Information on Prohibited Noxious and Noxious Weeds

A useful source of information and assistance with plant identification is the 2012 Alberta Invasive Plant Identification Guide. Or visit the Alberta Invasive Species Council Site for fact sheets. There is also a new app for iPhones to assist with weed identification and reporting.

Don’t despair. When you have to dig up a favourite because it is on the list, there are alternatives you can try. The brochure at this link suggests a number of plants of similar colour texture, size, etc that may fill that gap.

Updated 2021-02-27