Black Knapweed
Centaurea nigra L.
Family: Asteraceae
Description and life cycle
Black knapweed is a perennial with branching stems growing 20 - 80 cm tall. Plants reproduce
from a woody root crown and lateral roots. Prostrate growing stems may develop roots at their
nodes when they come in contact with moist soils. Broad basal leaves have stalks and shallow
lobes. Stem leaves are clasping and progressively become smaller towards the top of the plant.
Rose to lavender coloured flowers appear from July to October. The round, broad blooms are
produced individually at stem tips and measure 1.3 cm tall by 1 cm wide. Overlapping, fringed,
comb-like bracts are dark brown or black and bare a likeness to "ticks". About 60 ivory, linear-striped
seeds, 4 mm long with short pappus are produced in each head.
British Columbia Biological control agent
References
Pacific Northwest Extension Publication. No Date. Idenfication of knapweeds and starthistles
in the Pacific Northwest. Washington State Univer., Oregon State Univ., Univer. Idaho and U.
S. Dept. Agric. PNW432. 23 p.
Wilson, Linda M. and Carol Bell Randall. Biology and biological control of knapweed.
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