- Common Knapweed (Centaurea nigra)

- Aka Black Knapweed . Hairy perennial of grassy places. Widespread and common. Grooved stems branch towards the top. Leaves narrow, slightly lobed near base of plant. Flower heads 20 to 40mm across and with brown bracts and purple florets, appear June to September. Height up to 1mCommon Knapweed ( Centaurea nigra ). Hairy perennial of grassy places. Widespread and common. Grooved stems branch towards the top. Leaves narrow, slightly lobed near base of plant. Flower heads 20 - 40 mm across and with brown bracts and purple florets, appear June - September. Has smaller heads than the similar Greater Knapweed , with leaves that are undivided A very common pernnial of grassy places; tall (up to about 2 ft ) with blue thistle-like flower heads and narrow-oval leaves.