Submodule 5: Most Common Western Rangelands Weeds

Spotted Knapweed

Spotted knapweed (Centaurea maculosa), a biennial forb, forms a low-growing rosette with deeply lobed leaves following germination. After a few weeks, it bolts to form 1-20 flowering stems that are 8 inches to 4 feet (0.2 to 1.2 m) in height. Most of the branching of these stems occurs in the upper half. Stem leaves are covered with short, fine whitish or grayish hairs; the lower leaves are lobed while the upper leaves are smaller and have fewer lobes. Composite flowers (that have many small florets on one inflorescence) are about 0.75 in (2 cm) in diameter and 0.5 in (1.5 cm) tall and are produced throughout the summer months. Florets are whitish, pink, or light purple. Bracts are not spiny but have narrow, dark-tipped projections that give this plant its common name of spotted knapweed.

(photo courtesy Larry Howery)