Plants 15-60+ cm. Stems proximally usually glabrous, sometimes piloso-hirsute and/or stellate-pubescent, distally usually glabrous, sometimes stellate-pubescent. Leaves: basal 0(-2), cauline (5-)8-15(-45+); blades lance-elliptic to lanceolate, (20-)50-100(-150) × (10-)15-25(-40+) mm, lengths (3-)5-10+ times widths, bases cuneate to rounded or truncate (then sometimes ± clasping), margins usually toothed (to laciniate), denticulate, or entire (often ± revolute, at least distally), apices obtuse to acute, faces glabrous or ± stellate-pubescent, sometimes ± scabrellous (especially at or near distal margins). Heads (1-)5-30(-100+) in corymbiform to subumbelliform arrays. Peduncles usually stellate-pubescent. Calyculi: bractlets 9-15+. Involucres campanulate to hemispheric, (8-)9-11+ mm. Phyllaries 12-21+, apices rounded to acute, abaxial faces usually glabrous, rarely piloso-hirsute and/or stipitate-glandular. Florets 30-80+; corollas yellow, 10-18 mm. Cypselae columnar, 2.5-3.5 mm; pappi of 50-60+, stramineous to sordid bristles in ± 2 series, 6-7 mm.
The circumscription of Hieracium umbellatum adopted here is supported by research done by others, especially G. A. Guppy (1978) and E. Lepage (1960). Hieracium canadense var. kalmii (Linnaeus) Scoggan, referable here, is an illegitimate name.
Similar to no. 12 [Hieracium kalmii L.] and passing into it; lvs mostly 4-12 times as long as wide, scarcely or not at all clasping, often narrowed to the base, ±copiously provided, at least marginally, with short, stiff, blunt, subconic hairs, as well as generally ±stellate; peduncles commonly also with short, stout, subconic hairs scarcely if at all surpassing the stellate puberulence; 2n=18, 27. Thickets, open woods, and beaches; circumboreal, in Amer. s. to P.E.I., N.B., Mich., Minn., Colo., and Oreg.; disjunct to Spruce Knob, W.Va. July- Sept. (H. scabriusculum; Amer. plants possibly to be recognized as a distinct var., but the nomenclature recondite)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Infrequent in the lake area in very dry, sandy soil, on slopes wooded with black and white oak and on open dunes and rarely in a prairie habitat. Young's report from Jefferson County should no doubt be referred to some other species.