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Giant knotweed
Photo Credit: Leslie Mehrhoff, University of Connecticut, Retrieved from Bugwood.org (Image Number: 5447655), used under CC BY 3.0 US, modified from the original

Common Name: Giant Knotweed

Scientific Name: Fallopia sachalinensis

Habitat: disturbed areas, grassland wet, forests - wet areas, forests - open areas, forest edges, ditches

Provincial Designation: Prohibited Noxious

Prohibited Noxious weeds are plant species that are designated as "prohibited noxious" in the Alberta weed regulation. Prohibited noxious weeds must be destroyed, meaning all growing parts need to be killed or the plant's reproductive mechanisms need to be rendered non-viable.

Origin

Giant knotweed is native to northern Japan. It was introduced into North America as an ornamental due to its size and white flower clusters.

Legislated Because

This species forms dense stands that shade and crowd out native vegetation causing a loss or alteration of wildlife habitat, especially along waterways. It can also sprout through asphalt and small cracks in concrete causing structural damage to foundations and roads.

Description

Giant knotweed has small white flowers that are 3-5 mm wide and are clustered together in showy often upright sprays along the branches.

The large leaves are heart-shaped and grow up to 45 cm long and 40 cm wide. The undersides of leaves are covered in soft, 0.2-0.6 mm long hairs.

The stems are round and hollow and grow up to 4 m tall.

Learn more about this species:

SeeFact Sheets - Alberta Invasive Species Council

For More Information

Weed Management

Telephone

In Edmonton: 311

Outside Edmonton: 780-442-5311

Email invasiveweeds@edmonton.ca

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