Dipsacus sylvestris Huds.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stout, taprooted biennial (or short-lived, monocarpic perennial) 0.5–2 m, the stem increasingly prickly on the angles above; lvs ± prickly, especially on the midrib beneath, otherwise smooth or nearly so, the basal ones oblanceolate, crenate, generally dying early in the second season, the cauline lanceolate, to 3 dm, becoming entire upwards, commonly connate at base; heads erect, ovoid or subcylindric, 3–10 cm, on long naked peduncles; involucral bracts upcurved, unequal, the longer ones surpassing the heads; receptacular bracts ending in a conspicuous stout straight awn; cal silky, 1 mm; cor slender, hairy, 10–15 mm, the tube whitish, the short (1 mm) lobes generally pale purple; fr 5 mm; 2n=16, 18. Roadsides and waste ground, especially in moist low places; native of Europe, now a widespread weed in N. Amer. July–Sept.
common teasel, wild teasel