Carduus L.
Flower heads in terminal clusters
Stems discontinuously spinous-winged, naked just below the terminal flower heads. Heads ovoid, 2–3 cm diam. Florets pink or white. Widespread. Weed of cultivation, pastures and waste places. Introd. from Europe. Fl. spring–summer. Shore or Slender Thistle Carduus pycnocephalus
Stems continuously spinous-winged. Heads cylindrical, c. 2 cm long. Florets purple. Annual up to 1 m high. Widespread. Weed of cultivation, pastures and waste places. Introd. from Europe. Fl. spring–summer. Winged Slender Thistle Carduus tenuiflorus