Annuals or biennials, 20-70+ cm; fibrous-rooted (caudices relatively short, weak). Stems 1 (striated, frequently hollow, often pink- to purple-tinged), glabrous or leaf axils sparsely tomentose. Basal leaves (and proximal cauline) obscurely petiolate; blades obovate to oblanceolate, sometimes lyrate (lateral lobes to 5 pairs, terminal lobes larger than laterals), 50-150+ × 10-30+ mm, bases tapering, ultimate margins crenate to irregularly undulate. Cauline leaves gradually reduced (weakly clasping, similar to basal). Heads 8-30+ in umbelliform or cymiform arrays (robust plants with multiple arrays). Peduncles bracteate, glabrous or bases tomentose. Calyculi conspicuous (bractlets 2.5-4 mm). Phyllaries (13-)21, green, 5-7 mm, glabrous. Ray florets (8-)13; corolla laminae 7-9 mm. Disc florets 35-50+; corolla tubes 2.5-3.5 mm, limbs 2-3 mm. Cypselae 1-1.5 mm, sparsely hirtellous on ribs or glabrous; pappi 3-4 mm. 2n = 46. Flowering (Feb-)mid Mar-late May. Open wet areas, edges of woodlands, stream banks, roadsides, meadows, marshes, fallow fields; 0-600 m; Ala., Ark., Fla., Ga., Ill., Ind., Kans., Ky., La., Miss., Mo., Nebr., N.C., Ohio, Okla., S.C., Tenn., Tex. Packera glabella is common and almost weedy in wet, partially shaded places. The hollow, striated stems of P. glabella are distinctive.
Fibrous-rooted, mostly single-stemmed annual or winter- annual 1.5-8 dm, glabrous or obscurely floccose-tomentose in the axils; lvs mostly once pinnatifid (or in part twice pinnatifid) with generally rounded teeth and lobes, or the basal sometimes merely round- toothed, the largest ones at or near the base of the stem, to 20 נ7 cm, progressively reduced upward; heads ±numerous, the disk 5-10 mm wide; invol 4-6 mm, its bracts ca 21 or 13; rays 5-12 mm; achenes minutely hairy or glabrous; 2n=46. Moist, open or shaded places, often a weed in low fields; N.C. and Ky. to Fla., w. to S.D. and Tex., and adventive n. to s. Ont. May-July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.