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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

Are invasive plants taking over your yard?

gardeninvasivesAfter a cool wet spring, summer has finally arrived and many gardens are starting to showcase their blooms. Cooler conditions this spring in many areas of the province have helped invasive plants to thrive. While spring planting is likely complete, it’s still a good idea to grow plants that benefit the environment in your garden. You probably already know that certain plants are not native to your area; but some of these plants are invasive species which, in addition to not being native, also have the potential to cause economic and environmental harm. This harm comes from the fact that invasive species prey on native species and/or out-compete them for scarce resources.

Invasive plants can also decrease the amount of biodiversity in an area because the predators that would normally prey on plants in their native range do not exist in a non-native environment, allowing the population of non-native plants to grow rapidly.

So which plants are invasive, and how do you get rid of them without harming the environment?

First of all, which plants are invasive species depends on where you live, so make sure you check with a trustworthy resource to determine which plants are not native to your area. The simplest way to do this is to contact your regional invasive plant coordinator. There are a dozen regional groups across BC that are working hard to reduce the impacts of invasive plants and species in your area. To find a regional coordinator near you, access the online map through the ISC website. They are a helpful resource for information, volunteer opportunities, and ways to learn about invasive plants and responsible gardening practices.

Some examples of invasive plants of concern in BC include orange hawkweed (Hieracium aurantiacum), spotted knapweed (Centaurea biebersteinii), sulphur cinquefoil (Potentilla recta), and giant hogweed (Heracleum mantegazzianum). Giant hogweed is becoming more prominent in the Lower Mainland, Fraser Valley, Gulf Islands, and central to southern Vancouver Island due to the cool spring conditions, and is especially bad not only for the environment but because it has a toxic sap that can burn and blister the skin. Once exposed to this toxin, the area of skin affected can be uv-sensitive for several years to come, and if it contacts the eyes, it can cause blindness. This plant is so dangerous that Worksafe BC has a video for safety procedures. Giant hogweed can be confused with native cow parsnip, but giant hogweed has a very large umbrella-like umbel and can grow upwards of 5 meters! It is best NOT to touch or go near this plant if you spot it. For more information about giant hogweed and other invasive plants of provincial concern, click here.

While plants like giant hogweed should be removed carefully based on recommended practices or use of experts for removal, weeding is typically the simplest way of getting rid of invasive species, although it can be rather time-consuming. It is effective for invasive plants such as English ivy (Hedera helix), which resists pesticides and herbicides with its waxy coating. This plant can be gotten rid of by cutting any climbing vines, pulling out the roots with a garden shovel, and putting a deep layer of mulch over the area where it grows. This area should also be monitored in the spring to make sure no new shoots sprout. 

There are some invasive plants that grow more aggressively with weeding or mowing, such as orange hawkweed, and that’s way it’s important to learn more about invasive plants impacting your property and the best methods of removal and disposal. It’s almost always best not to compost invasive plants. Instead, bag and incinerate them at the local landfill. It’s even better if you label the bag and put in the appropriate place so these plant fragments don’t also spread to natural areas around the landfill and beyond. 

Volunteering with organizations to help stop invasive species in your area is also a good idea. You may make new friends and get some exercise at the same time! Your regional coordinator can link you to events like community weed pulls and other groups active in your area.

It is also a good idea to choose native species for your yard as much as possible. Native species require less maintenance than non-native species because they are by definition ideally adapted to the environment that they are already in. They can also attract local wildlife to your area, which increases the health of your ecosystem. Enjoy summer gardening!

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