Spotted Knapweed

(Centaurea stoebe L.)

(synonyms:  Centaurea biebersteinii and Centaurea maculosa)

Asteraceae (Sunflower Family)

▲ seedling

▲ first year rosette of compact, deeply lobed leaves

▲ ▼ mature plants with stiff, gray stems, deeply divided gray-green leaves and pinkish-lavender flower heads

▲ flowering (top) and non-flowering (lower front) portions of a spotted knapweed plant

▲ Close up of flowering stems

▲ ▼ flowers

▲ flower bud showing characteristic black tips of floral bracts

Spotted Knapweed: (pp. 98-99, Weeds of the Great Plains; pp. 126-127, Weeds of the Northeast)

·         biennial weed with grey-green, divided lower leaves, linear upper leaves; basal rosette has deeply divided leaves

·         leaves very hairy  with grayish appearance; bracts under inflorescence have dark spots at tips

·         grows 1-4' tall, forming much branched inflorescence structures

·         flowers rose-pink, small in June-August

·         found on roadsides, pastures, cultivated areas, non-crop areas

·         fairly rapidly increasing populations of spotted knapweed in southwest Missouri

·         other relatives of spotted knapweed are:

·         diffuse knapweed  (mentioned on p. 99, Weeds of the Great Plains)

o        biennial with leaves similar to spotted knapweed

o        has white flowers and comb-like toothed bracts under inflorescence

o        not found here, yet, but common near & west of Rocky Mountains

o        allelopathic

·         Russian knapweed (pp. 100-101, Weeds of the Great Plains)

o        Creeping perennial with creeping roots that can form dense colonies

o        Flowers pinkish-purple, similar to spotted knapweed

o        Leaves not deeply divided—just somewhat lobed or toothed

o        Bracts under inflorescence are papery

o        Also found in western plains & west of Rocky Mountains