Diffuse Knapweed

Centaurea diffusa

Asteraceae (Sunflower family)

Class B Noxious Weed

Control or Containment Required

Diffuse knapweed, a Class B noxious weed in Franklin County, arrived in the U.S. as a contaminant in alfalfa from the Caspian Sea region of Turkistan. This invader competes with desirable plants for nutrients, light and moisture.

A tap-rooted biennial or short-lived perennial, it has an upright stem that produces several spreading branches that upon maturity have a rounded form. Flowers are typically white but are sometimes pink or lavender. Flower bracts are tan colored, fringed with slender spines. 

Reproduction occurs primarily by wind-dispersed seeds. A single plant can produce as many as 18,000 seeds.