Knapweed, Spotted


Spotted Knapweed (Centaurea stoebe L. subsp. Micranthos) 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 around it. Early detection and rapid response 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. Is considered very invasive and is on the noxious plant list in most states. Control is only possible early before patches develop.

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