Field Guide to Noxious and Other Selected Weeds of British Columbia

Fourth Edition, 2002
Prepared by:

Roy Cranston and David Ralph
B.C. Ministry of Agriculture
 Dr. Brian Wikeem
 Previously with: 
 Silviculture Branch
 B.C. Ministry of Forests



Weeds are responsible for reductions in crop yield and quality and they lead to environmental degradation through destruction of native plant and animal habitat. Weeds also harbour insects and diseases of crops, create unsafe conditions, reduce property values and the aesthetics of an enjoyable landscape and many can poison humans, livestock and wildlife.

This field guide has been prepared to help farmers, ranchers, resource managers and the public identify British Columbia's noxious weeds. Some of the more common nuisance weeds that interfere with human activities are also detailed. Proper identification of problem weeds is the crucial first step in gaining knowledge about these troublesome plants so that a well planned control strategy can be developed.

As an aid in separating noxious species, all weeds legislated under the B.C. Weed Control Act are organized alphabetically by most common name at the beginning of the guide. Weeds classified as noxious throughout the entire Province are arranged first, followed by weeds classified as noxious within regional boundaries. Other selected nuisance weeds are arranged alphabetically following the regional weeds.

B.C. Weed Control Act
Noxious Weeds - Everybody's Problem

Noxious weeds are typically non-native plants that have been introduced to British Columbia without the insect predators and plant pathogens that help keep them in check in their native habitats. For this reason and because of their aggressive growth, these alien plants can be highly destructive, competitive and difficult to control.

The B.C. Weed Control Act imposes a duty on all land occupiers to control designated noxious plants.

The purpose for the Act is to protect our natural resources and industry from the negative impacts of foreign weeds.

The Following Weeds are Classified as Noxious within all Regions of British Columbia: Part I - Provincial

Annual Sowthistle (Sonchus oleraceus)
Canada Thistle (Cirsium arvense)
Crupina (Crupina vulgaris)
Dalmatian Toadflax (Linaria dalmatica)
Diffuse Knapweed (Centaurea diffusa)
Dodder (Cuscuta spp.)
Gorse (Ulex europaeus)
Hound's-tongue (Cynoglossum officinale)
Jointed Goatgrass (Aegilops cylindrica)
Leafy Spurge (Euphorbia esula)
Perennial Sowthistle (Sonchus arvensis)
Purple Nutsedge (Cyperus rotundus)
Rush Skeletonweed (Chondrilla juncea)
Scentless Chamomile (Matricaria maritima)
Spotted Knapweed (Centaurea maculosa)
Tansy Ragwort (Senecio jacobaea)
Velvetleaf (Abutilon theophrasti)
Wild Oats (Avena fatua)
Yellow Nutsedge (Cyperus esculentus)
Yellow Starthistle (Centaurea solstitialis)
Yellow Toadflax (Linaria vulgaris)

The Following Weeds are Classified as Noxious Within the Boundaries of the Corresponding Regional Districts: Part II-Regional

Blueweed Echium vulgare Cariboo, Central Kootenay, Columbia-Shuswap, 
East Kootenay, Okanagan-Similkameen, Thompson-Nicola
Burdock Arctium spp. Bulkley-Nechako, Cariboo, Columbia-Shuswap, Fraser-Fort George, Kitimat-Stikine, North Okanagan, Okanagan-Similkameen, Peace River, Thompson-Nicola
Cleavers Galium aparine Peace River
Common Bugloss Anchusa officinalis Kootenay-Boundary
Common Tansy Tanacetum vulgare Bulkley-Nechako, 
Central Kootenay, Columbia-Shuswap, 
East Kootenay, 
North Okanagan
Field Scabious Knautia arvensis Bulkley-Nechako, Kootenay-Boundary,  Thompson-Nicola
Green Foxtail Setaria viridis Peace River
Hoary Alyssum Berteroa incana Kootenay-Boundary
Hoary Cress Cardaria spp. Columbia-Shuswap, 
North Okanagan, Thompson-Nicola
Kochia Kochia scoparia Peace River
Marsh Plume Thistle Cirsium palustre Bulkley-Nechako, Fraser-Fort George
Meadow Knapweed Centaurea pratensis Columbia-Shuswap
Night-Flowering Catchfly Silene noctiflora Peace River
Orange Hawkweed Hieracium aurantiacum Bulkley-Nechako, 
Central Kootenay, Columbia-Shuswap, 
East Kootenay, Thompson-Nicola
Oxeye Daisy Chrysanthemum leucanthemum Cariboo, North Okanagan, Thompson-Nicola, Peace River
Perennial Pepperweed Lepidium latifolium East Kootenay, Thompson-Nicola
Plumeless Thistle Carduus acanthoides Central Kootenay
Puncturevine Tribulus terrestris Okanagan-Similkameen
Purple Loosestrife Lythrum salicaria Comox-Strathcona (by regional district bylaw)
Quackgrass Agropyron repens Peace River
Russian Knapweed Acroptilon repens North Okanagan
Russian Thistle Salsola kali Peace River
Scotch Thistle Onopordum acanthium North Okanagan
Sulphur Cinquefoil Potentilla recta Columbia-Shuswap, North-Okanagan, Okanagan-Similkameen, Thompson-Nicola
Tartary Buckwheat Fagopyrum tataricum Peace River
White Cockle Lychnis alba Peace River
Wild Chervil Anthriscus sylvestris Fraser Valley
Wild Mustard Sinapsis arvensis Peace River

The Following Common Nuisance Weeds are Not Regulated by the BC Weed Control Act:

Annual Bluegrass (Poa annua)
Baby's-Breath (Gypsophila paniculata)
Barnyardgrass (Echinochloa crusgalli)
Bladder Campion (Silene cucubalus)
Bog Rush (Juncus effusus)
Broad-Leaved Plantain (Plantago major)
Bull Thistle (Cirsium vulgare)
Common Chickweed (Stellaria media)
Chicory (Cichorium intybus)
Corn Spurry (Spergula arvensis)
Creeping Buttercup (Ranunculus repens)
Cudweed (Gnaphalium uliginosum)
Curled Dock (Rumex crispus)
Field Bindweed (Convolvulus arvensis)
Foxtail Barley (Hordeum jubatum)
Western Goat's-Beard (Tragopogon dubius)
Giant Hogweed (Heracleum mantegazzianum)
Groundsel (Senecio vulgaris)
Hemp-Nettle (Galeopsis tetrahit)
Henbit (Lamium amplexicaule)
Himalayan Balsam (Impatiens glandulifera)
Field Horsetail (Equisetum arvense)
Japanese Knotweed (Polygonum cuspidatum)
Lady's-Thumb (Polygonum persicaria)
Lamb's-Quarters (Chenopodium album)
Common Mallow (Malva neglecta)
Showy Milkweed (Asclepias speciosa)
Mullein (Verbascum thapsus)
Nightshade (Solanum species)
Nodding Beggar-Ticks (Bidens cernua)
Nodding Thistle, a.k.a. Musk Thistle (Carduus nutans)
Pineappleweed (Matricaria matricariodes)
Redroot Pigweed (Amaranthus retroflexus)
Scotch Broom (Cytisus scoparius)
Sheep Sorrel (Rumex acetosella)
Shepherd's-Purse (Capsella bursa-pastoris)
Spiny Annual Sow-thistle (Sonchus asper)
St. John's-Wort (Hypericum perforatum)
Stinkweed (Thlapsi arvense)
Cluster Tarweed (Madia glomerata)
Water Hemlock (Cicuta douglasii)
Wild Buckwheat (Polygonum convolvulus)
Witchgrass (Panicum capillare)


The following agencies and individuals are gratefully acknowledged for providing photographs: B.C. Ministry of Agriculture; B.C. Ministry of Forests; Washington State University; Washington State Noxious Weed Control Board, University of Idaho; University of Arizona; Mountainview Ecological Services; Michael Betts, Don Blumenauer, Bruce Brolley, Roy Cranston, Jack Freeman, Vippen Joshi, Bill McCloskey, Alistair McLean, Robert Needham, Rosamund Pojar, George Powell, David Ralph, Dave Riendeau, Ben Roche, Dean Swan, Loal Vance, Brian Wikeem, John Woods.

The information in this guide has been obtained from a number of sources including: Weeds of Canada, Weeds of the West, The Arable Weeds of Europe, Vascular Plants of the Pacific Northwest, Vascular Plants of British Columbia, The Thistles of Canada and The Biology of Canadian Weeds.


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