Plant 5-30 dm, glabrous or minutely granular-hairy; basal lvs oblanceolate or broader, mostly toothed, 0.5-7 cm נ2-15 mm; peduncles conspicuously inflated for some distance below the heads; invol 4-7 mm, its 10-22 bracts narrow; achenes 1.5-2 mm, often slightly rugose as well as strongly ribbed, otherwise glabrous, shining; 2n=18. Fields and waste places; native of Europe, but found occasionally from N.S., N.B., and Me. to Pa., O., and Mich., perhaps not becoming fully established. June-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.