Common Knapweed
Common Knapweed in grassland
Flower from above
Side view - swollen stem
Rayed form
Confusable - Great Burnet & Common Knapweed
Upper leaves
Upper and lower leaves
Pollination by bees
Centaurea nigra subsp. nigra
Asteraceae
Black Knapweed, Hardheads, Paintbrush
June to September
It is found throughout the country.
See the BSBI distribution map for Common Knapweed
It is found on grassland, sea-cliffs, scrub and waste
ground, by paths, roads and railway, and around woods
and fields,
Common Knapweed is a native, variable, stiff, perennial
herb growing up to 90cm (usually shorter).
Flowerheads have purple-pink individual tubular disc
florets in the form of a brush.
Enlarged outer florets give some flowerheads a rayed
look.
Subsp nemoralis, Lesser Knapweed, which predominates in
the south of the country, almost always the rayed form.
The dark triangular bracts give the flowerheads the
characteristic hardhead name.
They can be superficially confused with Great Burnet
flowerheads.
Leaves are lanceolate, alternate and pale green.
Lower leaves may be toothed.
Stems are ridged, stiff and swollen below the flowerhead.
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Common Knapweed in grassland
Flower from above
Side view - swollen stem
Rayed form
Confusable - Great Burnet & Common Knapweed
Upper leaves
Upper and lower leaves
Pollination by bees
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