Invasive Plants BC

Invasive Plants

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  Canada thistle (Cirsium arvense) is a root-creeping perennial. Considered noxious under the BC Weed Control Act, this thistle is commonly found on roadsides, cultivated fields, pastures, logged forests, riverbanks, and other disturbed areas. It is a major concern in the Peace River, Omineca and Skeena areas, and is a widespread throughout the province. Canada thistle has purple or white flowers, with stalkless, spiny, dark-green leaves, growing to 0.3-2 metres in height at maturity. Canada thistle spreads rapidly through horizontal roots that give rise to large infestation patches nearby and out-competing native plants. Canada thistle develops seeds sparingly and may produce 1,000 to 1,500 seeds per flowering shoot. Best adapted to rich, heavy loam, clay loam, and sandy loam, it grows poorly in shaded conditions, can tolerate saline, wet, or dry soils, but does not tolerate waterlogged or poorly aerated
  (Tanacetum vulgare) Common tansy (Tanacetum vulgare) is a perennial and considered regionally noxious under the BC Weed Control Act. Common tansy is currently distributed in the following areas: Bulkley-Nechako, Central Kootenay, Columbia-Shuswap, East Kootenay, and North Okanagan Regional Districts, and within Greater Vancouver, Fraser Valley, southeast coast of Vancouver Island, Gulf Islands, Sunshine Coast, and Squamish/Pemberton.Common tansy has yellow disc flowers that resemble buttons in a flat-topped cluster at the top of the plant. With fern-like leaves, common tansy can grow 0.4–1.5 metres in height at maturity.Spread mainly through seeds and roots, common tansy can be transported by birds, animals, and on vehicles that have been in infested areas. Seeds can remain viable for up to 25 years; therefore, stopping seed spread is a main concern. Common tansy prefers sunny areas with well-drained soil, and often infests stream
  (Heracleum mantegazzianum) Giant hogweed (Heracleum mantegazzianum), also known as “Giant Cow Parsnip,” is a perennial and currently distributed in the Lower Mainland, Fraser Valley, Gulf Islands, and central to southern Vancouver Island.Giant hogweed has numerous small white flowers clusters in an umbrella-shaped head, with stout, hollow green stems covered in purple spots. Dark green leaves are coarsely toothed in 3 large segments with stiff underside hairs, and lower leaves can exceed 2.5 metres in length. Giant hogweed can grow up to 5 metres in height at maturity.Giant hogweed is a highly competitive plant due to vigorous early-season growth, tolerance of full shade and seasonal flooding, as well as its ability to co-exist with other aggressive invasive plant species. Each plant can produce up to 100,000 winged seeds (typically 50,000) that remain viable in the soil for up to
  (Ulex europaeus) Gorse (Ulex europaeus) is a spiny, perennial evergreen shrub, considered noxious under the BC Weed Control Act, and thrives on sunny clearings with dry, infertile soil such as sandy or rocky areas, roadsides, fields and pastures, bluffs, cutblocks, and cutbanks. It is currently distributed in Vancouver Island, West Vancouver, some of the Gulf Islands, and Skidegate on the Queen Charlotte Islands. Gorse is a dense evergreen shrub with a single upright stem, spine-like leaves, and fragrant yellow, pea-like flowers. Seedpods are hairy and black. Gorse can grow 1-3 metres in height at maturity.Growing rapidly for the first 15 years, gorse can live up to 45 years. Maturing seedpods explode and disperse up to 18,000 seeds per mature plant. Gorse seeds are easily distributed by ants, animals, birds, and machinery. Since gorse grows mainly by the ocean,
  (Hieracium spp.) Hawkweeds (Hieracium spp.) are perennial plants with 14 non-native species recorded in BC, and are difficult to identify among the 8 native hawkweed species. One of the 14 non-native species, orange hawkweed (Hieracium aurantiacum) is currently the only hawkweed considered regionally noxious under the Weed Control Act. Most hawkweeds have yellow flowers. Invasive hawkweeds are found throughout most forest regions and regional districts in British Columbia. The regional districts east of the Rocky Mountains, Northern Rockies, and Peace River Regional Districts only have a few known invasive hawkweed sites and efforts to prevent further establishment and spread are actively underway. Orange hawkweed is regionally noxious in the East Kootenay, Central Kootenay, Columbia-Shuswap, Thompson-Nicola, Bulkley Nechako, and Cariboo Regional Districts. Hawkweeds have bright orange, orange-red, or yellow ray flowers with several flower heads in clusters at the
Himalayan blackberry (Rubus discolor) is mostly a biennial plant, growing on disturbed sites, along roadsides and rights-of-ways, in pastures, along river and stream banks, fresh-water wetlands, riparian areas, forest edges, and wooded ravines. They are currently distributed on the Lower Mainland, Sunshine Coast, Fraser Valley, Gulf Islands, central to southern Vancouver Island, Queen Charlotte Islands, the Okanagan, and the West Kootenay areas. Himalayan blackberry has petite, white or faint pink flowers with 5 petals, arranged in clusters of 5-20. Flower stalks are prickly, with robust stems (canes) that support large, flattened and hooked or straight prickles. Canes grow up to 3 metres in height and 12 metres in length at maturity. Evergreen leaves are predominantly large, rounded or oblong, and generally grouped in fives on first-year canes and threes on second year, flowering canes. Fruits are up to 2 cm
  (Berteroa incana) Hoary alyssum (Berteroa incana) is an annual to short-lived perennial. Considered regionally noxious under the BC Weed Control Act, hoary alyssum is most common on sandy or gravelly soils and establishes on roadsides, railway embankments, and heavily grazed pastures. It is currently found in south-central and southeastern BC including the Okanagan, Cariboo, Boundary, Thompson, and Kootenay areas.Hoary alyssum has small white flowers with deeply notched petals that are supported on slender stalks. The whole plant is covered in star-shaped hairs that are rough to touch, with grey leaves that clasp closely to the stem. Oval seedpods are chambered and held close to the stem with each chamber containing 5-7 black seeds. Hoary alyssum can grow up to 0.7 metres in height at maturity.Hoary alyssum spreads rapidly through a long season of seed production. Each plant flowers
  (Cynoglossum officinale) Hound’s-tongue (Cynoglossum officinale) is a biennial to short-lived perennial, and is considered noxious under the BC Weed Control Act. Hound’s-tongue is found on dry pasture, roadsides, and logged forestland. Found primarily in the southern interior of BC, it is a major concern in the Kootenay, Okanagan, Thompson, and Cariboo areas.Mature hound’s tongue plants have a woody taproot, with rough, hairy, wide leaves and dull reddish-purple, five-petal flowers. Each flower produces four rounded-triangular seeds covered with hooked prickles. Growing 0.5-1.2 metres tall, stems leaves are short and stalkless. First year plants form a rosette with leaves hanging down to resemble the shape of a dog’s tongue.Each plant produces 2,000-4,000 barbed seeds a year that cling easily clothing, livestock and wildlife, resulting in new infestations spread over great distances. Hound’s-tongue decreases forage production on rangeland and pastures. Barbed
  (Polygonum spp.) Knotweeds (Polygonum spp.) are invasive perennials, with four species found in British Columbia: Japanese knotweed (Fallopia japonica); Bohemian knotweed (Fallopia x bohemica); Giant knotweed (Fallopia sachalenensis); and Himalayan knotweed (Polygonum polystachyum). Knotweeds thrive in roadside ditches, low-lying areas, irrigation canals, and other water drainage systems. They are also found in riparian areas, along stream banks, and in other areas with high soil moisture. Knotweeds occur in the southwest coastal region, the Shuswap, Kitimat, Stikine, Skeena, Columbia, Okanagan, and Kootenay areas, as well as the Queen Charlotte Islands. Additional plants may exist in many gardens in communities across BC.Knotweeds have small white-green flowers that grow in showy, plume-like, branched clusters along the stem and leaf joints. Hollow stems stand upright and are bamboo-like with reddish-brown speckles and thin, papery sheaths. Leaves are heart or triangular-shaped on all

Other Invasive Organisms

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Common Carp. Text.
Didymo (Didymosphenia geminate) or “Rock Snot” is a fresh water diatom most commonly found in high elevation streams and rivers throughout northern Europe and North America. It has long been considered a ‘cold-water’ algae, but has since spread to warmer lower elevation streams and rivers. It can form massive blooms causing significant negative impact to freshwater fish, plants and invertebrates through habitat and food web alteration.   Its most distinguishing feature is a slimy brown layer or ‘ blooms’ that smothers rocks, aquatic plants or any other structures in the water.  The blooms resemble thick slimy looking mats and are distinguished from other forms of algae by its brown, beige or white color.  Didymo is never green in colour.   Although Didymo looks slimy in appearance, it is spongy and scratchy to the touch and has a texture similar to
The Eastern grey squirrel (Sciurus carolinensis) may be cute and fuzzy to on-lookers, especially in the popular tourist areas of Stanley Park in Vancouver, but it is an invasive mammal in British Columbia that is ranked by the Invasive Species Specialist Group (ISSG) as one of the Top 100 Invasive Species in the world. This small mammal has some big ecological impacts—it has depleted populations of the European red squirrel through out-competition and disease (parapoxvirus), and displaces native birds of their nesting habitat, eating the birds’ eggs and nestlings. It also competes with native mice and voles. Economically, Eastern grey squirrels cost homeowners repairs due to digging up of lawns and gardens, chewing through electrical wires, eaves and shingles, and nesting in roofs, attics, and chimneys. Fruit and nut trees and vines may not produce as well due to the
Largemouth Bass  
The New Zealand mud snail is a very tiny aquatic snail (often smaller than your baby fingernail) and is native to fresh waterbodies in New Zealand. The New Zealand mudsnail is typically light to dark brown in colour but may look black when wet. The shell of adult mud snails usually have 5 – 6 whorls that lean to the right, are less than 5 mm in size and can easily be confused with other fresh water and native snails. It is thought that the New Zealand mudsnail was transported to North America in the ballast water of transport ships originating from Europe and Asia. It was first recorded in North America in the late 1980’s in Idaho’s Snake River and is now widespread in many states including Washington, Oregon, and California. The New Zealand mudsnail can live in a
Appropriately named for its ‘fire’ like sting, the European fire ant (Myrmica rubra) will attack aggressively if disrupted. When this ant attacks, it pinches down with its mandible then swings around and stings multiple times. In a few cases it has produced severe allergic reactions including anaphylactic shock. The European fire ant is a small red to brownish red ant that can be identified by its two waist segments, our native ant only has one, and the two backward pointing spines and stinger (visible with a magnifying glass).  This invasive insect was introduced from its native Eurasia to eastern North America. It was first sighted along the eastern seaboard of the United States in the early 1900s and has since spread across several Canadian provinces including Nova Scotia, New Brunswick, Quebec, Ontario, and into British Columbia. European fire ant nests

Feature Article: History

The History of Invasive Plants in BC: How did they get here?

One of the greatest joys of traveling can be returning home with souvenirs for friends and family. Today’s travelers tend to purchase luxury items, while the first European settlers in British Columbia traded livestock and feed, plants, seeds, and other essentials for basic survival. This early movement of goods included the transfer of plants with beneficial characteristics into BC, but also those with invasive tendencies. Though unforeseen during early settlement, invasive plants now pose a significant threat to the environment, society, and economy.

Many of the goods imported by settlers became staples of the Canadian agriculture sector including forage crops such as corn and wheat. Unfortunately, among these beneficial exotic plant species also came invasive plants.

Invasive plants are commonly referred to as “alien,” “non-native,” or “introduced” plant species because they were brought to BC from other areas without their natural predators that would otherwise keep their populations in check. Aggressively out-competing native plants, invasive plants permanently alter fragile ecosystems, destroy wildlife habitat, harm human health and safety, and cost natural resource industries and taxpayers millions of dollars every year in management and control. So how did this problem evolve?

Records of invasive plants are limited, but indicate that since the 17th century, European settlers transported thousands of plants to North America for medicinal, agricultural, and ornamental uses.

The progression of invasive plants into BC began with the fur trade of the early 1800s. For instance, fur-trade gardens were established at Stuart Lake in 1811, Fort Langley in 1827, and Fort Thompson in 1842. These gardens may have contributed to the transfer of invasive plants and seeds to new areas of the province, either unintentionally in hay and other livestock feed products, or sold deliberately as ornamentals for flower gardens.

The highly invasive plant, Purple loosestrife (Lythrum salicaria) was introduced to BC as an ornamental, and has now spread rapidly through prolific seed production and trade among gardening enthusiasts. It has invaded wetlands, replacing diverse native vegetation with dense monocultures, thus impacting wildlife that depend on these wetland ecosystems for foraging, nesting, and breeding habitats.

As well as ornamental uses, invasive plants were introduced for medicinal benefits. For example, common burdock’s (Arctium minus) brownish-green, deep roots are used as a traditional medicinal herb and remedy for dry and scaly skin conditions such as psoriasis and eczema, and as a blood purifier clearing the bloodstream of toxins. In traditional Chinese medicine, burdock is often used with other herbs to treat sore throats and colds.

Despite some positive medicinal uses, burdock is now considered highly invasive as its burs cling to livestock and wildlife, causing irritation to eyes, throat, mouth, or the inside of the stomach. Infestations also reduce crop quality and desirable grazing vegetation, and are responsible for tainting milk products if grazed in large quantities.

In addition to ornamental and medicinal uses, invasive plants were brought to BC on overseas vessels for erosion control along early highway corridors. An example of this was described in the writings of explorer Captain Walter Grant in 1850 in which Scotch broom (Cytisus scoparius) seeds were obtained from the Sandwich Islands of Hawaii and brought to Vancouver Island. About three plants were introduced in Sooke, and infestations now colonize much of southern Vancouver Island. Consequently, these original plantings now pose serious problems for sight lines and require exhaustive maintenance to control.

Scotch broom is also a serious competitor to conifer seedlings; Douglas fir plantation failures in Oregon and Washington have been credited to dense infestations. During the spring bloom, Scotch broom causes allergy symptoms in people.

The environmental, economic and social consequences of introducing invasive plants
were not foreseeable to settlers of the 19th century, especially with the discovery of gold that drove a fever of activity and settlement in the province during the Gold Rush of 1858-1866. This dramatic increase in movement of people and resources became a key pathway for invasive plants. The Gold Rush brought approximately 30,000 people, 20,000 cattle, innumerable sheep, horses, and even camels to BC, resulting in the town of Barkerville, and marked trade routes, transportation corridors, roadhouses, farms, and ranches in the Cariboo region.

Since invasive plants quickly capitalize on disturbed, open ground, any newly formed trail, roadway, tilled farmland, and even the railway became key vectors for their introduction and establishment. One of North America’s earliest floral colonizers, Canada thistle (Cirsium Arvense), arrived in contaminated hay and grain seed. Canada thistle and knapweed (Centaurea spp.) infestations, as well as other invasive plants, are now known to cause a reduction in forage crop yields by as much as 15 percent and significant economic losses to BC farmers and ranchers, according to the Ministry of Agriculture and Lands.

As early as the 19th century, invasive plants like thistles were being recognized as problem plants. The first weed legislation in the new Province of British Columbia (1871) was the Thistle Prevention Act of 1877. This act refers to “perennial thistles” with no specific species identified, but was the first attention by government to restrict the movement of goods that were harming healthy farm and ranch production. The Noxious Weeds Act in 1888 listed eight species, with the purpose of preventing the spread of noxious weeds or invasive plants. The BC Weed Control Act has since replaced the Noxious Weeds Act and currently includes 48 noxious weeds. Recent provincial legislation that governs the management of invasive plants also includes the Community Charter Act, Forest and Range Practices Act, and the Integrated Pest Management Act.

Research into invasive plant identification and cultural control methods for invasive plants began in the 1920s, with the first course on weed identification at the University of British Columbia (UBC). UBC also developed a “Weed Science” course in the 1950s that was among the first of its kind in Canada.

Management practices to combat invasive plants began in the 1940s with chemical control. The BC Ministry of Highways began spraying knapweed along roadsides in 1967, and the BC Ministry of Forests began chemical control of knapweed on Crown land in the East Kootenays in 1969.

The use of biological agents evolved as an alternative control method, involving detailed screening, propagation, field release, redistribution, and monitoring of agents. The use of biological agents began in 1951, when Chrysolina beetles were successfully introduced on the invasive plant, St. John's-wort (Hypericum perforatum), near Edgewood, BC. Since then, more than 70 biocontrol agents have been released on 21 invasive plant species in BC.

As more research was conducted and management undertaken, results began to indicate an alarming trend: without management, invasive plants would exponentially increase and could cause irreversible damage to surrounding ecosystems, agricultural lands, and communities. These findings drove subsequent coordination and collaboration in the 1970s and mid-1980s to include expanded programs at UBC and other universities, innovative research by Agriculture Canada, and six new biocontrol agents for knapweed were made available by 1984 through the BC Ministry of Forests. Current collaborations involve efforts by more than a dozen regional invasive plant councils and committees, the Invasive Plant Council of British Columbia, all levels of government, private industry, the natural resource sector, non-government organizations, First Nations, and concerned individuals to minimize the impacts of invasive plants and prevent new infestations.

After more than 150 years since original introductions, increased transport, trade, travel, and tourism activities that form today’s global marketplace are bringing an unprecedented number of invasive plants to Canada and BC. As native plant communities are replaced by invasive plant infestations, biodiversity declines and habitats change. Improved collaboration among land managers, academia, industry, and government, as well as public awareness of invasive plants, will help to reduce their introduction and spread.

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