Invasive plants in Alberta: Urban Areas

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 What is the problem? | Species to watch out for | What you can do | General principles and resources
Land owners and occupiers are responsible for controlling noxious weeds and destroying prohibited noxious weeds under the Alberta Weed Control Act. Listed plants in the Act cause problems for the environment, health or economy. Know your responsibilities under the Act. Regardless of where plants are located, prevention is always the most effective approach in dealing with invasive plants.

What is the Problem?

Despite living in urban areas, many Albertans are fortunate enough to have extensive natural areas around them, including parks, forests, ravines, wetlands and river valleys. These areas provide dwellers the opportunity for closer contact with nature, but are also vulnerable to invasion by non-native plants.

Invasive plants can escape from gardens and landscape plantings, or they can be brought in from other parts of the province in soil, on vehicles or by wind and water.

Invasive plants can hamper the enjoyment of recreational areas – no one wants to hike in a field of thistles. Such invasive plants choke out native plants and wildflowers and thus, change the use of natural areas.

Species to Watch for
  • Some plant invasions originated as escaped ornamental plants:
  • Himalayan balsam (Impatiens glandulifera)
  • dame’s rocket (Hesperis matronalis)
  • yellow clematis (Clematis tangutica)
  • creeping bellflower (Campanula rapunculoides)
  • orange hawkweed (Hieracium aurantiacum)
Others invaders originated from agricultural fields:
  • Canada thistle (Cirsium arvense)
  • leafy spurge (Euphorbia esula)
  • common tansy (Tanacetum vulgare)
  • field scabious (Knautia arvensis)
  • hound’s-tongue (Cynoglossum officinale)
  • ox-eye daisy (Leucanthemum vulgare)

Himalayan balsam (Impatiens glandulifera)

Pale yellow iris (Iris pseudacorus), purple loosestrife (Lythrum salicaria) and flowering rush (Butomus umbellatus) were previously available for water gardens, but these species can become very invasive in streams and wetlands.

Creeping bellflower (Campanula rapunculoides)

Dame's Rocket (Hesperis matronalis)

Garlic mustard (Alliaria petiolata) is used as a herb, but is very invasive in forests and was recently discovered at three separate locations in the Edmonton area.
Some shrubs previously used for landscaping such as common buckthorn (Rhamnus cathartica) and saltcedar
(Tamarix spp) can also become invasive in natural areas.

What You Can Do
  • Watch out for unfamiliar plants when you are walking or cycling in urban parks and natural areas, and report them to park staff if you think they might be invasive.
  • Keep to established trails when walking or cycling in natural areas to reduce disturbance and the spread of plant seeds.
  • Keep dogs on a leash except in approved off-leash areas – sticky or spiny seeds like burdock or hound’s-tongue can be carried on their fur.
  • Do not plant “wildflower” seed mixes: many of these contain invasive plants. Many Alberta growers can provide native trees, shrubs, grasses, and wild flowers.
  • Do not compost invasive plants or dump garden waste or compost anywhere outside the garden fence.
  • Hand pull or dig out small patches of invasive plants before they go to seed or start to spread. Volunteer with community groups that organize invasive plant control events like weed pulls.
  • Remove and dispose of seed from pets, clothing, recreational equipment and vehicles.

Orange hawkweed (Hieracium aurantiacum)

Canada thistle (Cirsium arvense)

Purple loosestrife (Lythrum salicaria )

Garlic mustard (Alliaria petiolata )

Leafy spurge (Euphorbia esula)

Common tansy (Tanacetum vulgare)

Field scabious (Knautia arvensis)

Hound’s-tongue (Cynoglossum officinale)

Ox-eye daisy (Leucanthemum vulgare)

Pale yellow iris (Iris pseudocorus)

Flowering rush (Butomus umbellatus)

General Principles and Resources Learn More

Find out more on this topic and access these additional resources at the following web page:
  • Invasive Weed Factsheets
  • A Landowner’s Guide to Managing and Controlling Invasive Plants
  • Invasive Plant Prevention and Management (City of Calgary)
Source: Agdex 640-16. February 2014.

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For more information about the content of this document, contact Chris Neeser.
This document is maintained by Jennifer Rutter.
This information published to the web on August 25, 2014.
Last Reviewed/Revised on August 21, 2018.