What’s the Difference Between Spotted, Brown, Black, and Meadow Knapweed?

By CELESTINE DUNCAN, TechLine Editor

Twenty two different knapweed (Centaurea sp) species are well established in the United States. Four of these knapweed overlap in distribution and share similar morphological characteristics. This includes spotted (C. stoebe), brown (C. jacea), black (C. nigra) and meadow knapweed (C. xmoncktonii). The key to separating these and other knapweed species are the involucre bracts.1 These four knapweed spread by seed, but brown, black, and meadow knapweed can also spread from woody root crowns.

 
Spotted Knapweed
(C. stoebe)
Photo Celestine Duncan
Spotted Knapweed
  • Native to Eurasia
  • Biennial or perennial; tap root
  • 8 to 48 inches tall
  • Leaves: basal leaves 1-2 times divided into lobes; 4 in. long and 1.2 in. wide; upper leaves linear entire2 or only once lobed and smaller
  • Flower: pink to purple, sometimes white
  • Bracts: black tipped bracts, tip and upper margin have soft, spine-like fringe; center spine shorter than others (see inset image)
  • Spread by seed
  • Management
Spotted Knapweed Distribution
Black Knapweed
(C. nigra)
Photo by Joe DiTomaso, Univ of Cal.–Davis, Bugwood.org
Black Knapweed
  • Native to western Europe
  • Perennial; woody root crown
  • 8 to 32 inches tall
  • Leaves: basal leaves broadly lance-shaped, becoming smaller up the stem
  • Flower: rose to lavender
  • Bracts: oval-shaped with broad, comb-like, dark brown or black fringed margins; fringe length up to 3X as long as bract width (see inset image
  • Spread by seed and woody root crown
  • Management
Black Knapweed Distribution
Brown Knapweed
(C. jacea)
Photo Cindy Roche, Bugwood.org
Brown Knapweed
  • Native to Eurasia
  • Perennial; woody root crown
  • 20 to 48 inches tall
  • Leaves: basal leaves lance-shaped up to 6 in. long, becoming smaller up the stem
  • Flower: rose to purple, rarely white
  • Bracts: somewhat hairy, broad, thin papery margins; center of bract is dark brown (see inset image)
  • Spread by seed and woody root crown
  • Management


Brown Knapweed Distribution
Meadow Knapweed
(C. ×moncktonii)
Photo by Eric Coombs, Ore. Dept of Ag., Bugwood.org
Meadow Knapweed
  • Hybrid: brown X black knapweed
  • Perennial; woody root crown
  • 20 to 40 inches tall
  • Leaves: Basal leaves lance-shaped, up to 6 in long; upper leaves smaller and entire 2
  • Flower: rose to purple, rarely white
  • Bracts: light to dark brown, roundish, thin papery margin with fringes about equal width of bract center (see inset image)
  • Spread by seed and woody root crown
  • Management

Meadow Knapweed Distribution
 
 

1. Involucre bracts are small leaf- or scale-like structures surrounding an inflorescence, located just below flower petals.
2. "Entire leaf margins" refers to leaves that are neither toothed, lobed, nor compound, i.e. simple with smooth margins.