Biennials or perennials, 20-60+ cm; rhizomatous and/or fibrous-rooted (bases erect to suberect), sometimes stoloniferous (mostly eastern populations). Stems 1 or 2-3, clustered, floccose-tomentose proximally and in leaf axils, otherwise sparsely tomentose or glabrescent. Basal leaves (and proximal cauline) petiolate; blades narrowly elliptic to elliptic-ovate or oblanceolate to suborbiculate or sublyrate, 20-70+ × 10-30+ mm, bases tapering to rounded or abruptly contracted, margins subentire to crenate, serrate-dentate, or pinnately lobed (abaxial faces floccose-tomentose, especially along midribs, ± glabrescent). Cauline leaves gradually reduced (petiolate, sublyrate or pinnatisect, abaxial faces sparsely hairy; distals sessile, subentire to irregularly dissected). Heads 6-20+ in open or congested, corymbiform arrays. Peduncles conspicuously bracteate, sparsely to densely tomentose. Calyculi inconspicuous. Phyllaries 13 or 21, green (tips sometimes cyanic), 5-6+ mm, densely tomentose proximally, glabrescent distally. Ray florets 8-10; corolla laminae 9-10 mm. Disc florets 60-70+; corolla tubes 2.5-3.5 mm, limbs 3.5-4.5 mm. Cypselae 1.5-2.5 mm, usually hirtellous, sometimes glabrous; pappi 6.5-7.5 mm. 2n = 46, 92. Flowering mid Apr-early Jun(-mid Jul, north). Prairies, meadows, open wooded areas, along highways, railroads, around mining and construction areas, usually on limestone; 50-1800 m; Ont., Sask.; Ark., Colo., Ga., Ill., Ind., Iowa, Kans., La., Mich., Minn., Miss., Mo., Mont., Nebr., N.Mex., N.Dak., Ohio, Okla., Pa., S.Dak., Tenn., Va., Wis., Wyo. Packera plattensis is abundant, widespread, and almost weedy. Putative hybrids with other species are known. Plants in mesic, remnant prairies in the east are sometimes stoloniferous.
Biennial or short-lived perennial 2-7 dm from a short caudex, sometimes also stoloniferous, ±persistently floccose-tomentose until flowering time or later, at least as to the stem, lower lf-surfaces, and invols; basal lvs narrowly or broadly elliptic or ovate to suborbicular or broadly oblanceolate, crenate-serrate or some deeply lobed, the blade and petiole to 10 נ3 cm; cauline lvs conspicuously reduced upwards, becoming sessile, ±pinnatifid; heads several or rather many, the disk 6-12 mm wide; invol 4-6 mm; achenes usually hirtellous; 2n=44, 46. Prairies and other dry, open places; Great Plains, and irregularly e. to s. O., Tenn., N.C., and Va., mostly inland from the coastal plain. May-July. Passes into nos. 6 [Senecio tomentosus Michx.] and 8 [Senecio pauperculus Michx.].
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
©The New York Botanical Garden. All rights reserved. Used by permission.