Invasive aquatic plants

Eurasian watermilfoil (Myriophyllum spicatum)

Place of origin

• Originally from Eurasia and North Africa, it was introduced to North America in 1961 in Lake Erie, Ontario. To our knowledge, Eurasian watermilfoil is currently not present in Alberta.

Habitat

• Prefers shallow water, but can root up to 10 m in depth.

Identification

• Perennial, submersed; flowers are very small, reddish and held above water on a flower spike.
• Usually 12 to 21 closely spaced leaflet pairs per leaf.
• Feather-like leaves collapse around stem when out of water.

Reproduction

• A single segment of stem and leaves can form a new colony. Plant does produce seeds but germination rates are usually poor. Stem fragmentation and underground runners allow this plant to reproduce rapidly.

Issues

• Forms large, floating mats that prevent light penetration into waterbodies, out-shading native plants and reducing oxygen levels when decomposing.
• Out-competes native milfoils.

Related information

• Quick Facts: Eurasian Water Milfoil
• Fact Sheet – Native Vs. Invasive Milfoil (PDF, 588 KB)

Flowering rush (Butomus umbellatus)

Place of origin

• Originally from Eurasia, it was introduced as an ornamental garden plant in the 1890s. Flowering rush is now found across Canada and the United States.

Habitat

• Can grow as an emergent plant along shorelines or partially submerged in lakes and rivers up to 4 m in depth.

Identification

• A perennial, surviving winters and droughts.
• Cross section of leaves is triangular, while the flowering stem is round.
• Easiest to identify when flowering in summer months. Each umbrella-shaped cluster has whitish pink petals. Flowers are only produced in very shallow water or on dry sites.
• Looks similar to cattails (Typha latifolia), rushes (Juncus spp.) and bur-reeds (Sparganium spp.).

Reproduction

• Can reproduce by root system fragments or rhizome buds called bulbils. Seed production is yet to be observed in North American populations.

Issues

• Dense stands in irrigation ditches can reduce water availability, and in lakes can interfere with boat propellers and swimming.

Current management in Alberta

Alberta Environment and Parks has partnered with several organizations to study eradication methods on Lake Isle and Chestermere Lake.

Hand digging, mechanical harvesting, bottom barriers, diver assisted suction harvesting and herbicide treatments have all been tested in Alberta. Hand digging and herbicide treatments are the most feasible treatments, but they have their limitations with effort and approvals.

Herbicide applications to decrease the population and density of flowering rush were also used in Buffalo Creek near Innisfail.

Related information

• Flowering Rush Infographic (PDF, 1.4 MB)
• Blog (Let's Go Outdoors): Don't let this pretty plant fool you... it's an invasive species
• Map: Flowering Rush Distribution in Alberta
• Map: Lake Isle Flowering Rush Survey (PDF, 1.5 MB)
• Map (USDA Natural Resources Conservation Service): Flowering rush distribution across North America
• Quick Facts: Flowering Rush
• YouTube video: Impacts of Flowering Rush

Phragmites (Phragmites australis australis)

Place of origin

• Originally from Eurasia, it is unclear how this subspecies of phragmites was introduced to Canada. Phragmites australis australis was found in 2 locations in Alberta near Brooks in March of 2016 and has since been sighted in various other isolated locations.

Habitat

• Grows in shallow water, up to 1 m near the shore of still or slow moving water, such as that found in wetlands or ditches.

Identification

• Perennial with large stems up to 4 m tall.
• Alternating leaves, 25 to 50 cm long and 1 to 5 cm wide.
• Feathery seed head with several flowered spikelets that are 10 to 18 mm long.
• Identification is complicated by a native counterpart found in Alberta, Phragmites australis americanus. Due to similar appearance, DNA analysis is required to confirm species.

Issues

• Highly competitive and form dense stands, outcompeting native plants for water and nutrients.

Current management in Alberta

• Both stands of phragmites found in Alberta were treated in 2016. The terrestrial stand was treated with herbicides, while the stand in water was cut and burned.
• Control of phragmites can be difficult, especially once well established. Methods for control or eradication by trained personnel include a combination of cutting and/or burning, as well as chemical treatment.

Related information

• Quick Facts: Phragmites
• Map: Phragmites Distribution in Alberta

Himalayan balsam (Impatiens glandulifera)

Place of origin

• Native to India, it was likely introduced to North America as an ornamental plant. Himalayan balsam has been found in Alberta along water bodies.

Habitat

• Grows in moist, nutrient rich soil and thrives in disturbed riparian habitats and wet woodlands.

Identification

• Himalayan balsam leaves are simple, oblong-shaped with serrated edges, arranged oppositely on a square, hollow stem.
• Leaf veins and stems have red to purple tinges. Flowers are irregular with 5 purple to pink to white petals and resemble an English policeman's helmet.
• Round brown seeds are released explosively when a ripened capsule is disturbed or dried.

Reproduction

• It is only able to reproduce by seed; however, a single plant can produce up to 4,000 seeds that launch up to ten metres in all directions.

Issues

• Displaces native vegetation, reducing habitat for wildlife and native plants.
• Draws pollinators away from native plants.

Current management in Alberta

• Control of Himalayan balsam can be difficult, especially once well established. Methods for control or eradication by trained personnel include careful hand digging for isolated or small populations, repeated mechanical cutting, and chemical treatment. The objective for control is to repeatedly remove the plant before they set seed.

Related information

• Quick Facts: Himalayan Balsam

Pale yellow iris (Iris pseudacorus)

Place of origin

• Native to Africa, Asia and Europe and was likely introduced to North America as an ornamental plant. Pale yellow iris has already been found in isolated locations in Alberta.

Habitat

• Grows in wetlands or along waterbodies – it can grow in water up to 25 cm deep.

Identification

• Pale yellow iris leaves are long, dark green and sword-like with raised mid-ribs that are slightly off-centre; overlapping fan-like arrangement starting from the base.
• Flowers are white to yellow with distinct purple to brown markings.
• Flat brown seeds form in large, green triangular capsules.

Reproduction

• It is able to reproduce both by seed, easily dispersed by water, and through thick rhizome (root) fragments and bulbs.

Issues

• Pale yellow iris presents a human safety concern, as all parts of the plant are irritating to skin and poisonous to humans and animals if consumed.
• Infestations can displace native vegetation and alter water quality, reducing habitat for fish, wildlife and native plants.
• Dense rhizome mats in irrigation ditches, channels or storm water management ponds can increase sedimentation, disrupt the flow and availability of water and change wetlands to dry environments.

Current management in Alberta

• Control of pale yellow iris can be difficult, especially once well established. Methods for control or eradication by trained personnel include careful hand digging and benthic barriers for isolated or small populations, repeated mechanical cutting and chemical treatment. Burning is not recommended, as regrowth is expected.
• Care must be taken with hand digging and cutting to ensure all plant fragments are removed and disposed of. Fragments and seeds can drift with water movement and result in new infestations.

Related information

• Quick Facts: Pale Yellow Iris
• Map: Pale Yellow Iris Distribution in Alberta

Purple loosestrife (Lythrum salicaria)

Place of origin

• Native to Asia and Europe, it was likely introduced to North America as an ornamental plant. Purple loosestrife has been found in sporadic locations in Alberta. In the 1990s, a purple loosestrife eradication program in Alberta was successful in reducing the majority of locations in the province.

Habitat

• Prefer to grow in moist, highly organic soils and neutral to alkaline pH.

Identification

• Purple loosestrife leaves are slightly hairy, lance-shaped, and can be opposite or whorled.
• Flowers attach closely to the square, woody stem in a tall vertical spike; petals are pink to purple surrounding a yellow centre.

Reproduction

• It reproduces primarily by seed, producing more than 2 million seeds per plant annually but can also spread through stem cuttings and root fragmentation.

Issues

• Purple loosestrife infestations can displace native vegetation and alter water quality, reducing habitat for fish, wildlife and native plants.
• Dense, tall stands in irrigation ditches, channels or storm water management ponds can disrupt the flow and availability of water and eliminate open water habitats.

Current management in Alberta

• Control of purple loosestrife can be difficult, especially once well established. Methods for control/eradication by trained personnel include: careful hand-digging for isolated or small populations, repeated mechanical cutting and chemical treatment.
• Care must be taken with hand digging and cutting to ensure all plant fragments are removed and disposed of. Fragments and seeds can drift with water movement or animal dispersal and result in new infestations.

Related information

• Quick Facts: Purple Loosestrife
• Map: Purple Loosestrife Distribution in Alberta