Basal leaves: blades palmately 5-12-lobed or -angled, mostly 5-20+ × 5-20+ cm, margins irregularly denticulate. Cauline leaves mostly 5-25 mm. Calyculi: bractlets 5-15 mm. Phyllaries mostly 7-15 mm. Ray corollas: laminae (2-)4-10 mm. Disc corollas 10-12 mm. Cypselae 3-4 mm; pappi 8-12 mm, ± surpassing involucres. 2n = 60. Flowering spring-summer. Disturbed sites, sandy or rocky soils, calcareous sites; 0-800 m; introduced; Saint-Pierre and Miquelon; B.C., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Conn., Ill., Ind., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Tenn., Vt., Va., Wash., W.Va., Wis.; Eurasia. Flowering heads of Tussilago farfara close at night (laminae of ray corollas arch and roll inward). The species is becoming an invasive weed in some areas.
Rhizomatous perennial 0.5-5 dm, the cauline bracts ca 1 cm; lvs long- petioled, cordate to suborbicular, with deep narrow sinus, callous-denticulate and shallowly lobed, 5-20 cm long and wide, glabrous above, persistently white-tomentose beneath; heads at first cylindric, expanding with maturity, the disk to 3 cm wide; invol 8-15 mm; rays very numerous, narrow, not much exceeding the invol and pappus; 2n=60. Native of Eurasia, naturalized in disturbed and waste places in ne. U.S. and adj. Can., w. as far as Minn., and s. to Md., Va., and Ky. Apr.-June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.