*Centaurea solstitialis L.

Heads solitary. Involucral bracts with a spine 2–3 cm long, spinules palmately arranged. Basal leaves lyrate, up to 10 cm long; cauline leaves linear, decurrent, entire. Involucre urn-shaped, 1 cm diam. Cypselas compressed, brown, 2–3 mm long. Pappus bristles 5 mm long. Erect, white-tomentose annual up to 60 cm high. Widespread. Weed of cultivation, pastures and waste places. Introd. from the Mediterranean. Fl. chiefly summer. St Barnaby’s Thistle