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Alberta Invasive Plant Identification Guide

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Knapweed, Spotted<br />

Centaurea stoebe, Asteraceae (Sunflower Family)<br />

Category: Prohibited Noxious<br />

• Information: Introduced from Europe, covers vast areas of land in<br />

Canada and in the USA, found in disturbed areas, is allelopathic (toxic to-<br />

wards other plants).<br />

• Life cycle: Biennial or short-lived perennial.<br />

• Root: Taproot.<br />

•Leaves: Rosette leaves are deeply lobed, grayish green, and up to 15cm<br />

long. Stem leaves finely divided into linear segments.<br />

• Stems: Up to 120cm tall and highly branched.<br />

• Flower: One pinkish-purple flower head on each branch. Bracts have<br />

dark spot on tip and fringed edges.<br />

• Seed/Fruit: Black seeds 2mm long. Prolific seed producer.<br />

• Control: Long term, hand pick in rosette stage, chemical control before<br />

seed has set.<br />

Sarah Schumacher, Wheatland County<br />

Sarah Schumacher, Wheatland County<br />

34<br />

Montana State University <strong>Invasive</strong> <strong>Plant</strong> <strong>Identification</strong> <strong>Guide</strong> Montana State University <strong>Invasive</strong> <strong>Plant</strong> <strong>Identification</strong> <strong>Guide</strong>

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