Arctium minus Schkuhr
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - To 1.5 m, rarely more; lvs petiolate, the lower petioles mostly hollow, the blade narrowly to very broadly ovate, cordate at base, to 5 × 4 dm, thinly tomentose or eventually glabrate beneath, subglabrous above; branches of the infl ascending to widely spreading, racemiform or subthyrsoid, the heads mostly short-pedunculate or subsessile; invol 1.5–2.5 cm thick, glabrous or slightly glandular to sometimes evidently arachnoid-tomentose, usually a little shorter than the fls, greenish-stramineous or a little purplish, the inner bracts often more flattened than the others and scarcely hooked; achenes 4–5.5 mm; 2n=32, 36. Native of Eurasia, now established on roadsides and in waste places throughout most of the U.S. and s. Can.