Invasive Plant

Diffuse knapweed

Centaurea diffusa

About This Species

Diffuse knapweed plants can produce up to 18,000 seeds per year that can remain dormant in the soil for a long time. Seeds can be spread by wind, livestock, and people. Diffuse knapweed is often found growing open areas and well-drained soils where they establish in grasslands, open forests, and along roadsides – it is uncommon on cultivated land. They choke out desirable forage for livestock and wildlife and increase soil erosion.

How to Identify

Fine-textured Diffuse knapweed has hairy, greyish-green, split leaves on many branches growing from a single upright stem. The flowers are white or sometimes purple, with small, sharp, rigid spines on the bracts. Diffuse knapweed grows to 0.1 to 0.6 m. flowers are white, sometimes rose-purple or lavender, broadly urn-shaped, found in clusters or solitary at the end of branches. Bracts are yellowish with a brownish margin, sometimes spotted, fringed on the sides, and terminating in a slender bristle or spine. It has larger, hairy leaves at the base of the plant that get smaller as they go up the stem. Seeds are light brown to black in colour.


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Diffuse knapweed is a PlantWise "Alert" species - Gardeners should avoid purchasing or planting.

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