Spotted knapweed

September 16, 2015

Centaurea stoebe L. ssp. micranthos (Gugler) Hayek

Life cycle

Biennial or short-lived perennial.

Leaves

First-year leaves originate from a basal rosette, followed by a flowering stem in the second year. Basal leaves are deeply and irregularly lobed on long stalks; stem leaves are alternate and finely dissected. Leaves are grayish green and roughly hairy.

spotted knapweed leaf spotted knapweed rosette
Spotted knapweed upper leaf (left) and rosette (right).

Stems

Erect, wiry stems elongate during the second year, up to 6 feet tall with multiple branching. Stems are roughly hairy and often green to purple-striped.

spotted knapweed stem
Spotted knapweed stem.

Flowers and fruit

Terminal and axillary heads consist of purple to pink disk flowers above encircled by distinctly black-tipped bracts below. The seed is enclosed in a single-seeded, olive-green to brown fruit with a bristly pappus that can attach to animals for transport.

spotted knapweed flower
Spotted knapweed flower head.

Reproduction

Seeds.

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Related Topic Areas

Integrated Pest Management


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