It is a tall biennial or short-lived monocarpic thistle, forming a rosette of leaves and a taproot up to 70 cm long in the first year, and a flowering stem 1–1.5 m tall in the second (rarely third or fourth) year. The stem is winged, with numerous longitudinal spine-tipped wings along its full length. The leaves are stoutly spined, grey-green, deeply lobed; the basal leaves up to 15–25 cm long, with smaller leaves on the upper part of the flower stem; the leaf lobes are spear-shaped (from which the English name derives). The inflorescence is 2.5–5 cm diameter, pink-purple, with all the florets of similar form (no division into disc and ray florets). The seeds are 5 mm long, with a downy pappus, which assists in wind dispersal.