Don’t harbor criminals…Noxious Weeds in Alberta

Certain plants are illegal.

The government calls them ‘noxious’ weeds. These are invasive alien species that are a threat to agriculture and to natural ecosystems. Vegetable louts, they can elbow aside native species and can infiltrate agricultural crops. The result? Ecosystems lose biodiversity, and farmers need to use more herbicides. Let’s not let our gardens be a contributing factor to the spread of these plants.

Municipalities are concerned–visit the web sites for the cities of Edmonton and Calgary for what you can do to recognise and fight weeds. It is especially important for those of us who have a more relaxed style of naturalistic gardening–there have been cases of fuss-budget neighbours using the weed control act as a weapon against what they feel are slovenly gardens. Don’t let it happen to you.

The Alberta Invasive Plants Council has information on weeds and photographs on how to identify them. Go there now…you may be surprised to find that criminals that are lurking in your garden.

Some ornamental plants are not listed as invasive, but have the potential to spread. Avoid these plants, especially if you live on land that borders any natural areas. Even the Shasta daisy (Leucanthemum x superbum), a horticultural cultivar, can revert and hybridise with the ox-eye daisy, a noxious weed. If your Shastas are self-seeding, it is (ob)noxious.

The Alberta Weed Control Act governs noxious weeds. Weed Control Regulation lists the following: (Note that ‘prohibited noxious weeds‘ must be destroyed, while ‘noxious weeds’ must be controlled–i.e don’t let them go to seed or spread)

1. The following plants are designated as prohibited noxious weeds in Alberta. (I have colored the plants that I often find in home gardens here in Edmonton)

  • autumn olive — Elaeagnus umbellata Thunb.
  • balsam, HimalayanImpatiens glandulifera Royle
  • barberry, common — Berberis vulgaris L.
  • bartsia, red — Odontites vernus (Bellardi) Dumort
  • buckthorn, common — Rhamnus cathartica L.
  • cinquefoil, sulphur — Potentilla recta L.
  • crupina, common — Crupina vulgaris Pers. ex Cass.
  • dyer’s woad — Isatis tinctoria L.
  • Eurasian water milfoil — Myriophyllum spicatum L.
  • flowering rush — Butomus umbellatus L.
  • garlic mustard — Alliaria petiolata (M. Bieb.) Cavara & Grande
  • goatgrass, jointed — Aegilops cylindrica Host
  • hawkweed, meadow — Hieracium caespitosum Dumort.
  • hawkweed, mouse-ear — Hieracium pilosella L.
  • hawkweed, orange — Hieracium aurantiacum L.
  • hoary alyssum — Berteroa incana (L.) DC.
  • hogweed, giant — Heracleum mantegazzianum Sommier & Levier
  • iris, pale yellowIris pseudacorus L.
  • knapweed, bigheadCentaurea macrocephala Puschk. ex Willd.
  • knapweed, black — Centaurea nigra L.
  • knapweed, brown — Centaurea jacea L.
  • knapweed, diffuse — Centaurea diffusa Lam.
  • knapweed, hybrid — Centaurea × psammogena Gáyer
  • knapweed, meadow — Centaurea × moncktonii C. E. Britton
  • knapweed, Russian — Rhaponticum repens (L.) Hidalgo
  • knapweed, spotted — Centaurea stoebe L. ssp. micranthos(Gugler) Hayek
  • knapweed, squarrose — Centaurea virgata Lam. ssp. squarrosa (Willd.) Gugler
  • knapweed, Tyrol — Centaurea nigrescens Willd.
  • knotweed, giant — Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr.
  • knotweed, hybrid Japanese — Fallopia × bohemica (Chrtek & Chrtková) J. P. Bailey
  • knotweed, Japanese — Fallopia japonica (Houtt.) Ronse Decr.
  • loosestrife, purpleLythrum salicaria L.
  • medusahead — Taeniatherum caput-medusae (L.) Nevski
  • nutsedge, yellow — Cyperus esculentus L.
  • puncturevine — Tribulus terrestris L.
  • ragwort, tansy — Jacobaea vulgaris Gaertn.
  • rush skeletonweed — Chondrilla juncea L.
  • saltcedar — Tamarix ramosissima Ledeb.
  • saltlover — Halogeton glomeratus (M. Bieb.) C.A. Mey.
  • St John’s-wort, common — Hypericum perforatum L.
  • starthistle, yellow — Centaurea solstitialis L.
  • tamarisk, Chinese — Tamarix chinensis Lour.
  • tamarisk, smallflower — Tamarix parviflora DC.
  • thistle, marsh — Cirsium palustre (L.) Scop.
  • thistle, nodding — Carduus nutans L.
  • thistle, plumeless — Carduus acanthoides L.

The following plants are designated as noxious weeds in Alberta:

  • baby’s-breath, commonGypsophila paniculata L.
  • bellflower, creeping — Campanula rapunculoides L.
  • bindweed, field — Convolvulus arvensis L.
  • blueweed — Echium vulgare L.
  • brome, downy — Bromus tectorum L.
  • brome, Japanese — Bromus japonicus Thunb.
  • burdock, great — Arctium lappa L.
  • burdock, lesser — Arctium minus (Hill) Bernh.
  • burdock, woolly — Arctium tomentosum Mill.
  • buttercup, tall — Ranunculus acris L.
  • chamomile, scentless — Tripleurospermum inodorum (L.) Sch. Bip.
  • clematis, yellowClematis tangutica (Maxim.) Korsh.
  • cockle, white — Silene latifolia Poir. ssp. alba (Miller) Greuter & Burdet
  • daisy, oxeyeLeucanthemum vulgare Lam.
  • dame’s rocketHesperis matronalis L.
  • henbane, black — Hyoscyamus niger L.
  • hoary cress, globe-podded — Lepidium appelianum Al-Shehbaz
  • hoary cress, heart-podded — Lepidium draba L.
  • hoary cress, lens-podded — Lepidium chalepense L.
  • hound’s-tongue — Cynoglossum officinale L.
  • mullein, commonVerbascum thapsus L.
  • pepper-grass, broad-leaved — Lepidium latifolium L.
  • scabious, field — Knautia arvensis (L.) Coult.
  • sow thistle, perennial — Sonchus arvensis L.
  • spurge, leafy — Euphorbia esula L.
  • tansy, commonTanacetum vulgare L.
  • thistle, Canada — Cirsium arvense (L.) Scop.
  • toadflax, Dalmatian — Linaria dalmatica (L.) Mill.
  • toadflax, yellow — Linaria vulgaris Mill.

3 thoughts on “Don’t harbor criminals…Noxious Weeds in Alberta

  1. Hi Zone 3b:

    Thanks for this post. I’d been meaning to check out the new weed list, but got so bogged down in the legalese of the law that I never made it very far. The Alberta Invasive Plant Identification Guide is much more user friendly.

    Alas, I now know that the interesting mystery seedling with ciliated leaf margins that I have been nurturing the last few years is, or I should say was, a barberry. The barberry planted itself (presumably via a bird dropping), but others on the list came from such unlikely sources as the Devonian Botanical Garden, a seed catalog from New Brunswick, and – dare I say it – even a friendly naturalistic gardener!

    Only the Devonian seed source established in the garden (Bighead Knapweed must be new to the list), but it has a long, deep taproot and takes some grubbing. Well, got me out into the cold, grey, dreary Victoria Day garden anyway. Now I have room for something new and not prohibited.


    1. I just removed my Bighead (;)) yesterday. The only barberry I have are the Berberis thunbergii cultivars–not on the noxious list.
      I’m also eager to fill the empty spaces with something new. With todays chill and dampness, it’s a good time to read up on possible replacements.


  2. Thank you for this well-written post, presented in a clear, thoughtful manner. All education about invasives is extremely valuable…hopefully the word can be spread to every gardener in the province!


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