Knapwood

 

Common name: Spotted Knapweed

 

Growth form: Forb

 

Life Span: Biennial (or short - lived perennial)

 

Origin: Eurasia

 

Flowering Dates: June-September

 

Reproduction: Seeds

 

Height: 0.3 - 1.2 m (1-3.9 ft.)

 

Flower: Pink to purple or rarely white, all disk florets; marginal florets enlarged, falsely radiate (about 1.5 cm long)

 

Fruit: Achene (2.5 - 3.5 mm long), notched on one side of the base, brown to black; pappus a short tuft of bristles (2 - 3.5 mm long)

 

Seed: Enclosed in the achene, small

 

Leaves: Alternate; basal and rosette leaves narrowly elliptic to oblanceolate, usually 1 - 2 times pinnately parted or remotely dentate to entire; stem leaves (2 - 4 cm long) pinnately divided into remote and narrow segments (1 - 3 mm wide); upper leaves entire (1 - 2 cm long), nearly hairless to tomentose

 

Stems: Erect or ascending, 1 to several, branching above, ridged

 

Underground: Taproot, stout

 

Where Found: Primarily in north central and northeastern Nebraska on rangeland, meadows, and roadsides, especially in sandy soils

 

Uses and Values: Spotted knapweed has a bitter taste, but it is sometimes grazed by deer

 

Poisoning: None

 

Other: Spotted knapweed is a noxious weed in Nebraska and other states

 

Similar Species: Diffuse knapweed (Centaurea diffusa Lam.) is a noxious weed and has white to rose or purple flowers. Its involucral bracts are divided like teeth of a comb with a teminal spine (1.8 - 8 mm long). The bracts are usually not dark at the tip. Yellow starthistle (Centaurea solstitialis L.) is an annual with yellow ray and disk flowers and spines (11 - 30 mm long) on the involucral bracts