Weeds and plants

Dandelions and quackgrass aren’t the only weeds a gardener in Calgary needs to look out for – invasive ornamental plants can sometimes disguise themselves as pretty flowers and wreak havoc on our urban and wild landscapes. 

Weeds and plants to watch out for

Invasive ornamentals may look nice, but they choke other desirable garden species, take over flower beds and lawns, and spread rapidly between yards and parks. The province of Alberta regulates weeds under the Weed Control Act in 2 categories: Noxious and Prohibited Noxious.

In Calgary, the Early Detection Rapid Response (EDRR) program aims to prevent the spread of a priority list of invasive weeds through accurate identification and early intervention to minimize long-term environmental impacts and economic costs by targeting invasive species during their initial stage of establishment. These invasive plants not only have serious and unfortunate impacts on your immediate environment - they affect many areas of Calgary's economy and ecology. By encouraging the establishment and spread of these sneaky invaders, we risk:

  • Altering natural plant communities and reducing both animal and plant diversity.
  • Degrading bird, fish and wildlife habitats.
  • Changing water flow, availability and quality.
  • Increasing challenges to food production (including price hikes to compensate for increased weed control.)
  • Potentially reducing the aesthetic, tourism and property values of infested areas within the city.

That's why the City is shining a spotlight on EDRR species Calgarians need to be aware of.

Invasive plants to avoid in Calgary

Scientific Name Common Name(s) and Ornamental Varieties
Alliaria petiolata (M. Bieb.)  

Garlic mustard, garlic root, garglicwort, hedge garlic, Jack-by-the-hedge, poorman’s-mustard
Berteroa incana (L.) DC.

Hoary alyssum, hoary false madwort, hoary false alyssum
Butomus umbellatus L.

Flowering rush, grassy rush, water gladiolus
Centaurea jacea L.

Brown knapweed, common knapweed, hardheads, brown-ray knapweed
Centaurea × psammogena Gáyer

Hybrid knapweed
Cirsium palustre (L.) Scop.

Marsh thistle, marsh plume thistle, European swamp thistle
Daucus carota

Wild carrot, Queen Anne’s lace, bird’s nest, bishop’s lace, carrot flower
Fallopia japonica (Houtt.) Ronse Decr.

Japanese knotweed, Asian knotweed, elephant-ear bamboo, fleece flower, Japanese bamboo, wild rhubarb, donkey rhubarb
Impatiens glandulifera

Himalayan Balsam, policeman's helmet, Himalayan impatiens, ornamental jewelweed, kiss-me-on-the-mountain, Indian touch-me-not, Indian balsam, poor man's orchid
Iris pseudacorus L.

Pale yellow iris, yellow flag iris, water flag
Jacobaea vulgaris Gaertn.

Tansy ragwort, Stinking willies, staggerwort, tansy butterweed
Lepidium appelianum Al-Shehbaz

Globe-podded hoary cress
Lepidium draba L.

Heart-podded hoary cress
Lythrum salicaria L.

Purple loosestrife, purple lythrum, spiked loosestrife
Pilosella aurantiaca L.  

Orange hawkweed, king devil, orange-red king devil, devil’s paintbrush, red daisy flameweed orange paintbrush, orange aster
Pilosella caespitosa Dumort.

Meadow hawkweed, yellow hawkweed, field hawkweed
Rhamnus cathartica L.

Common buckthorn, buckthorn, European buckthorn
Thesium ramosum

Field thesium

If you spot one of these species in Calgary report it on the EDRR Report form.

Learn more about common pests in Calgary​

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