Invasive Plants

Canada Thistle (Cirsium arvense)

Canada Thistle has small purple or white flowers that grow in clusters of one to five at the top of the plant. The leavers are long, narrow, and alternate on the stem with crinkled deep loped, and spiny edits.

At maturity, this plant grows to 0.3 to 2 m tall. It reproduces by seed, but also spreads through creeping, horizontal roots. Canada Thistle is differentiated from all similar species by the lack of spines on the main stem, small flowers, and height (less than 2 metres tall)

English Holly (Ilex aquifolium)

English Holly is an evergreen tree with spiny dark green leaves and bright red berries. Flowers are whitish and have a sweet scent. English Holly grows rapidly up to 7 to 1o m in height, and adapts to shady and sunny conditions.

It often shades native plants depriving them of light. It consumes lots of water and its roots can out-compete forest species for nutrients and water. Seedlings are commonly found in mixed deciduous and coniferous forests around the south coast, along the edges of wetlands and especially near residential areas.

For more information on prevention and control, see this Fact Sheet on English Holly

English Ivy (Hedera helix)

English Ivy, was introduced from Europe and Asia and is an evergreen vine with waxy leaves about 5 to 10 cm long. The plant can grow up to 20 to 30 m high and is usually found growing up tree trunks and covering the forest floor.

Ornamental plantings are the key cause for widespread introduction of English Ivy into forests and other natural areas. English Ivy grows all year and because it is well-adapted to the Pacific Northwest climate, it out-completed many other plant species. When it grows up a tree, English Ivy can significantly degrade tree health and increase the risk of a treeing being blown over. It can also cause aesthetic and structural damage to walls, fences and other infrastructure.

For more information on prevention and control, see this Fact Sheet on English and Irish Ivies

Giant Hogweed (Heracleum mantegazzianum)

Giant Hogweed (also known as Giant Cow Parsnip) has large umbrella-shaped white flowers and can grow up to 5 m in height at maturity. This plant has dark green leaves that are coarsely toothed in three large segments with stiff underside hairs, and lower leaves can exceed 2.5 m in length.

With prolific seed capacity, producing up to 100,000 seeds per plant, Giant Hogweed can spread quickly, dominating native vegetation. If you find Giant Hogweed on your property, take special care during removal.

For more information on prevention and control, see this Fact Sheet on Giant Hogweed

Hedge Bindweed, or Morning glory (Calystegia sepium)

This persistent invasive plant is found twining around other plants and structures, often forming a tangled mass. It spreads by underground stems and roots can resprout from fragments left in the soil. For more information on prevention and control, see this Fact Sheet on Hedge Bindweed. 

Himalayan Blackberry (Rubus discolor)

Himalayan Blackberry is a European species of blackberry that was originally introduced for its fruit. This plant has small, white or faint pink flowers with 5 petals, arranged in clusters of 5 to 20. Canes grow up to 3 m in height and 12 m in length at maturity. The leaves are large, rounded or oblong.

Himalayan Blackberry out-competes low growing native vegetation and prevents the establishment of shade-intolerant trees. This plant often takes over stream channels and stream banks through shading and build-up of leaf litter and dead stems.

For more information on prevention and control, see this Fact Sheet on Himalayan Blackberry

Knotweed Species

Japanese Knotweed has small green-white flowers that grow in plumes off stem and lead joints. The stems are hollow and bamboo-like. They grow rapidly (up to 3 m per year) and spread quickly.

This plant take persistence and diligence to control. It spreads through root and stem fragmentation. Fragments as small as half an inch can form new plants. If you find Japanese Knotweed on your property, take special care to remove it.

For more information on prevention and control, see this Fact Sheet on Knotweeds

Orange Hawkweed (Hieracium aurantiacum)

Orange Hawkweed has bright orange flowers on a single, leafless stem that is covered in black hairs. The plant grows to approximately 0.3 m in height. This plant forms a dense ground cover, out-competes native plants, and provides no food or value to local wildlife.

Orange Hawkweed is a relatively new invader to the Metro Vancouver region. It has not been found in many places in Port Moody, but should be treated as quickly as possible so it is eradicated.

Policeman's Helmet (Impatiens glandulifera)

Policeman's Helmet, also known as Himalayan Balsam, is a tall plant with pink, white, and purple flowers. It can grow up to 2 m in height and has hollow stems with long, slender leaves and flowers shaped like and English policeman's helmet.

Policeman's Helmet will grow tall and dense, displacing other plants and leave bare soil prone to erosion with it dies back each fall. This is especially problematic in and around stream banks. Seeds are produced in tubular pods, which when mature, explode and can launch seeds up to 5 m away. Seedpods can split with little disturbance so significant care needs to be taken to remove the plant after it flowers. When the plant grows along watercourses, seeds can be propelled into the water and transported great distances.

For more information on prevention and control, see this Fact Sheet on Policeman’s Helmet

Purple Loosestrife (Lythrum salicaria)

Purple Loosestrife is a woody half-shrub, semi-aquatic perennial with a stiff four-sided set minding in dense purple flowers. It invades water areas at low-to-mid elevations, growing in ditches, irrigation canals, stream banks, lake and river shores, and tidal flats.

Purple Loosestrife can out-compete most native species, yet provides little local food value, cover or nesting material. Seeds remain dormant over winder and germinate the following spring or early summer or they can remain dormant for many years before sprouting.

For more information on prevention and control, see this Fact Sheet on Purple Loosestrife

Reed Canary Grass (phalaris arundinacea)

Reed Canary Grass is a cool season perennial grass with noticeable creeping rhizomes. It favours wet, poorly drained sites and may be found in ditches, along the edges of ponds and lakes, in marshlands, and in wet meadows.

This plant was introduced from Europe and Asia for ornamental use and mixed with native grass species. The result, is an aggressive offspring that has spread throughout the central and western region of North America. This mixture of native and invasive species has resulted in debate about the invasiveness and origins of the species in some regions.

For more information on prevention and control, see this Fact Sheet on Reed Canarygrass

Saltmeadow Cordgrass (Spartina patens)

Saltmeadow Cordgrass is an invasive foreshore grass that is spreading the Burrard Inlet and the Port Moody arm. Left uncontrolled, it can convert mudflats into monoculture grass stands, resulting in the loss of habitat for many species including migratory birds, shellfish, salmon, and other fish populations.

Scotch Broom (Cytisus scoparius)

Scotch Broom is an evergreen shrub with bright yellow, pea-like flowers that may have red markings in the middle. It grows from 1 to 3 m tall at maturity.

It invades rangelands, replacing forage plants, and is a serious competitor to conifer seedlings. High density infestations of Scotch Broom can reduce wildlife habitat, hinder vegetation of wetlands and upland sites, and increase wildfire fuel loads.

For more information on prevention and control, see this Fact Sheet on Scotch Broom

Yellow Flag Iris (Iris pseudacorus)

Yellow Flag Iris is a clumping perennial herb that grows 40 cm to 1.5 m tall, and is the only totally yellow-flowered iris in BC. This plant is often found in fertile, low-lying wetland habitats (riverbanks, ponds, lakes, marshes), and can grow in both salt water and fresh water.

Yellow Flag Iris is particularly bad for cattails, sedges, and rushes that are used by many birds for nesting. Plants need to be pulled or cut every year for several years to weaken and eventually kill the plant. Skin can be irritated by this plant, and gloves and appropriate clothing should be word during disposal.

Yellow Lamium (Lamium galeobdolon)

Lamium is a trailing, evergreen perennial groundcover with square stems and heart-shaped leaves. The Leaves are typically variated and slightly hairy. This plant has small, light-yellow flowers that bloom in mid-spring.

Lamium is a popular ornamental plant that is very aggressive and well adapted to growing in shaded and open areas. Seeds can be transported up to 70 m away from the parent plant. The plant also spreads with roots that smother native plants.