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Invasive Plant Details

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Russian Knapweed

Latin Name: Rhaponticum repens formerly Acroptilon repens

Priority Ranking: Regional EDRR

Identification

Flower: Pink to purple, thistle-like flower heads that bloom from late spring to summer.

Leaves: Lance-shaped, greyish-green, and slightly hairy with deeply lobed basal leaves.

Stems: Erect, stiff, and covered with fine hairs, growing up to 1 meter tall.

Growing Environment: Prefers dry, disturbed soils in pastures, roadsides, and waste areas.

Growth Habit: A perennial herb that spreads aggressively through creeping rhizomes and seeds, forming dense, long-lived colonies. It can dominate large areas and is difficult to eradicate. In situ, Russian knapweed appears as dense, tall stands with pinkish-purple flowers in disturbed areas.

Priority Ranking: Regional EDRR

Impacts on Environment

Impacts: Highly invasive, particularly in dry areas and pastures, where it can form dense monocultures.

Toxicity: Toxic to horses, causing irreversible neurological damage (chewing disease).

Photo Credits: freenatureimages.eu - Stan Stebbs