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Spotted Knapweed (Centaurea stoebe ssp. micranthos)

Spotted Knapweed gets its name from the tiny black triangular tipped bracts surrounding the flower heads.
Spotted Knapweed gets its name from the tiny black triangular tipped bracts surrounding the flower heads.

Spotted Knapweed is a biennial that produces up to 25,000 seeds that may remain in the soil for up to 8 years. It is a native plant of Europe and was brought to North America in the 1800's. Mature plants may grow to 3 feet in height. Flowering heads are pink to purple and appear from midsummer to fall.

Spotted Knapweed produces a natural herbicide called "catechin" that eradicates plants arount it. Early detection and rapid reponse are key elements in eradicating Spotted Knapweed. This noxious weed can be found in rangelands, dry meadows, pastures, upland rocky areas, roadsides and sandy or gravelly flooded plains of streams and rivers.

Approximately 100,000 acres currently infest Idaho.

Spotted Knapweed rosette showing last years dead stalk.
Spotted Knapweed rosette showing last years dead stalk.

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