Annual weed 0.5-2 m; stem glabrous below, strigose near the middle, commonly spreading-hirsute above; lvs chiefly opposite (only some of the reduced upper ones alternate), petiolate, lanceolate to broadly ovate, ±serrate, acuminate, 5-15 נ2-7 cm, scaberulous-strigose; infl of several or many spiciform branches, the heads practically sessile in the axils of reduced, ovate to lance- linear, conspicuously ciliate-margined lvs 5-20 mm; invol 2-3.5 mm, its bracts 3-5, subtending the achenes, sparsely long-hirsute, broad and ciliate distally; pistillate fls with tubular cor 1-1.5 mm tending to persist on the resinous-dotted achene, sometimes subtended by very slender and inconspicuous receptacular bracts; 2n=34. Waste ground, especially in moist soil; Ind. to N.D., s. to Miss. and N.M., and occasionally intr. eastward. Sept., Oct. (I. caudata; I. ciliata)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.