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, Himalayan — Impatiens 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 yellow — Iris pseudacorus L.
- knapweed, bighead — Centaurea 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, purple — Lythrum 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, common — Gypsophila 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, yellow — Clematis tangutica (Maxim.) Korsh.
- cockle, white — Silene latifolia Poir. ssp. alba (Miller) Greuter & Burdet
- daisy, oxeye — Leucanthemum vulgare Lam.
- dame’s rocket — Hesperis 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, common — Verbascum 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, common — Tanacetum vulgare L.
- thistle, Canada — Cirsium arvense (L.) Scop.
- toadflax, Dalmatian — Linaria dalmatica (L.) Mill.
- toadflax, yellow — Linaria vulgaris Mill.
