In recognition of National Invasive Species Awareness Week 2025, the B.C. Wildlife Federation is highlighting the growing threat of invasive species in B.C.’s wetlands. Since 1996, the BCWF has been a leader in wetland conservation, working to protect, restore, and spread the word about these critical ecosystems across the province.
Wetlands play a crucial role in maintaining healthy watersheds by filtering pollutants, storing carbon, reducing flood risks, and providing essential habitat for fish, amphibians, waterfowl, and countless other species. However, invasive plants and animals threaten their integrity by outcompeting native vegetation, altering water flow, reducing biodiversity, and increasing erosion. Without intervention, these invaders can severely degrade wetland function, making restoration efforts more difficult and costly.
This article highlights some of the most damaging invasive species affecting B.C.’s wetlands and provides guidance on how to identify, report, and control them before they take over.
Reed Canarygrass (Phalaris arundinacea)
Reed canarygrass is widespread in B.C., particularly in lowland floodplains, agricultural areas, and riparian wetlands, where it displaces native plants crucial for water filtration and wildlife habitat. This aggressive grass forms dense monocultures, reducing habitat diversity for fish, amphibians, and birds. It also alters water flow, increasing the risk of flooding and erosion, and lowers wetland productivity, making restoration efforts more challenging.
Origin:
Native to Europe and Asia, introduced to North America as a forage crop and for erosion control.
Identification:
- Found in wet meadows, ditches, floodplains, and shorelines
- Flat, rough-edged leaves (up to 2 cm wide) with a blue-green hue
- Forms dense, impenetrable stands, choking out native vegetation
- Grows up to 2 meters (6.5 feet) tall
- Purple-tinged, feathery seed heads that turn tan in late summer
Prevention and Control:
- Avoid using reed canarygrass in erosion control or landscaping—opt for native alternatives such as:
- Slough Sedge (Carex obnupta)
- Tufted Hairgrass (Deschampsia cespitosa)
- Sitka Willow (Salix sitchensis)
- Clean boots, gear, and equipment to prevent seed spread
- Shading with native trees or shrubs can reduce growth
- Mowing before seed production prevents spread but must be repeated
- Targeted herbicide use (in accordance with regulations) may be needed for large infestations under professional supervision
Additional Control Methods Being Trialed/Applied:
- Benthic barriers – These are specially designed aquatic mats placed over invasive plant beds to block sunlight, limit oxygen, and prevent root spread. Benthic barriers are typically anchored in place for several months to kill invasive plants by preventing photosynthesis
- Learn more in Additional Information and References at the bottom of this post
Yellow Flag Iris (Iris pseudacorus)
Yellow flag iris is expanding across lakeshores, ditches, and wetland margins in B.C., where it crowds out native plants, disrupts wetland hydrology, and threatens fish and waterfowl habitat. This species forms thick root mats, reducing water flow, increasing sediment buildup, and lowering oxygen levels in aquatic environments. Additionally, it is toxic to livestock and can harm aquatic species.
Origin:
Native to Europe, western Asia, and North Africa, introduced as an ornamental plant.
Identification:
- Grows 1-1.5 meters (3-5 feet) tall
- Sword-like green leaves growing in a fan shape
- Bright yellow flowers with drooping petals, blooming in late spring
- Thick underground rhizomes form dense root mats
Prevention and Control:
- Never plant yellow flag iris in gardens or near water, consider native species instead:
- Blue Flag Iris (Iris versicolor)
- Soft-stemmed Bulrush (Schoenoplectus tabernaemontani)
- Water Smartweed (Persicaria amphibia)
- Remove plant fragments from boats and gear
- Hand dig small patches, removing all rhizomes
- Cut and cover with plastic to prevent regrowth
- Targeted herbicide use (in accordance with regulations) may be needed for large infestations under professional supervision
Purple Loosestrife (Lythrum salicaria)
Purple loosestrife has become widespread along rivers, lakeshores, and ditches in B.C., where it displaces native wetland vegetation, alters floodplain hydrology, and threatens habitat for waterfowl, amphibians, and pollinators. It forms dense stands that reduce biodiversity, outcompeting native plants that provide food and shelter for wildlife. Over time, it changes wetland structure, affecting water retention and making flood events more severe.
Origin:
Native to Europe and Asia, introduced as an ornamental plant and for medicinal uses.
Identification:
- Grows 1-2 meters (3-6.5 feet) tall
- Square stems with opposite, lance-shaped leaves
- Spikes of bright purple flowers, blooming mid to late summer
Prevention and Control:
- Do not plant purple loosestrife—consider native species instead such as:
- Hardhack (Spiraea douglasii)
- Fireweed (Chamerion angustifolium)
- Blue vervain (Verbena hastata)
- Douglas aster (Symphyotrichum subspicatum)
- Hand-pull young plants before they go to seed
- Dispose of removed plants in sealed garbage bags (not compost)
- Biological control using beetles (Galerucella spp.) has been effective in some areas
American Bullfrog (Lithobates catesbeianus)
The American bullfrog has established populations in Vancouver Island and the Lower Mainland, where it outcompetes native frogs, preys on fish, birds, and small mammals, and spreads amphibian diseases like chytrid fungus. This highly adaptable species disrupts wetland food chains and can rapidly colonize new habitats, posing a serious threat to B.C.’s native amphibians.
Origin:
Native to eastern North America, introduced to B.C. through the pet and food trade.
Identification:
- Largest frog in North America (up to 20 cm or 8 inches long)
- Green-brown smooth skin with a lighter underside
- Lacks dorsolateral ridges (folds of skin running down the back)
- Deep call in summer resembling the bellow of a bull
Prevention and Control:
- Never release pet frogs into the wild
- Reduce artificial standing water to limit breeding
- Report sightings to local conservation groups so biologists can take professional control measures
Red-Eared Slider Turtle (Trachemys scripta elegans)
Populations of red-eared sliders have been found in urban lakes, wetlands, and slow-moving rivers, particularly in Metro Vancouver and the Okanagan. This invasive species competes with B.C.’s only native turtle, the western painted turtle (Chrysemys picta bellii), spreads disease, and disrupts aquatic ecosystems. Many red-eared sliders were released from the pet trade, contributing to their spread.
Western painted turtles are a species at risk in some areas of B.C., making competition with red-eared sliders a serious conservation concern. Preventing the release of pet turtles into the wild is critical to protecting B.C.’s native turtle populations.
Origin:
Native to the southeastern United States, introduced through the pet trade.
Identification:
- Medium-sized freshwater turtle with a slightly domed, olive-green shell, up to 30 cm (12 inches) long
- Distinct red stripe behind each eye
- Comparison to Western Painted Turtle:
- Size: Red-eared sliders grow up to 30 cm (12 inches), while western painted turtles reach about 25 cm (10 inches)
- Shell: Red-eared sliders have a domed shell with faint yellow markings; western painted turtles have a flatter, darker shell with red edges.
- Plastron (belly): Red-eared sliders have a yellow plastron with dark markings, while western painted turtles have a bright red or orange plastron with a distinct dark pattern.
Prevention and Control:
- Never release pet turtles—rehome them responsibly
- Do not feed or relocate wild turtles
- Report sightings to local conservation groups
Additional Information and References
Success! Using Benthic Barriers to Control Reed Canarygrass
Are you interested in invasive species management? Fighting a reed canary grass problem? Learn from the successes Dr. Catherine Tarasoff of Agrowest Consulting Scientists Ltd has seen in trials using benthic barriers to manage reed canary grass and learn about next steps for tackling this invasive species.
From Forage to Foe: The Environmental Impact of Reed Canarygrass Invasion – BCWF Watershed Team
Reed Canarygrass Fact Sheet – ISCBC
Profile – Yellow Flag Iris – ISCBC
Purple Loosestrife Profile and Resources – Invasive Species Centre
American Bullfrog Profile – ISCBC
BCWF Watershed Team 
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