Plants 50-150 cm (solitary or clustered); rhizomes creeping, elongate. Stems 1-10+, erect, proximally glabrous, increasingly puberulent distally into arrays. Leaves: basal 0; mid and distal cauline numerous (sometime 100+ per stem) , crowded, sessile or subsessile; blades linear-elliptic, mostly 50-120 × 6-12 mm, tapering at both ends, margins remotely serrulate or subentire, 3-nerved, faces glabrous or sometimes puberulent abaxially on midnerves. Heads 80-900+, in paniculiform arrays, branches recurved, secund. Peduncles 1-3 mm, sparsely strigose; bracteoles linear, 1-3. Involucres narrowly campanulate, 2-3 mm. Phyllaries in 3-4 series, linear-lanceolate, strongly unequal, midribs raised, enlarged apically, apices acute to usually obtuse or rounded, apically ciliate. Ray florets mostly 7-11, 1-2 × 0.1-0.2 mm. Disc florets 2-7; corollas 2-3 mm, lobes 0.4-0.6 mm. Cypselae (narrowly obconic) 1-1.5 mm, sparsely strigillose; pappi 2-2.5 mm. 2n = 18, 36. Flowering Jul-Sep. Riverbanks; 0-200+ m; Ind., Ky., Md., Pa., Tenn., Va. Solidago rupestris is similar to S. canadensis in head size but with fewer rays, and it is vegetatively more like S. gigantea. It is uncommon, occurring in a series of disjunct populations with an apparent gap between eastern and western areas of the range.
Stems 5-15 dm from long creeping rhizomes, glabrous below, slightly puberulent above the middle, more definitely so in the infl; lvs chiefly cauline, numerous, crowded, thin, triple-nerved, glabrous, or occasionally puberulent along the midrib and main veins beneath, remotely serrulate or subentire, sessile or subsessile, slender, tapering to both ends, mostly 5-12 נ0.6-1.2 cm; infl paniculiform, with recurved-secund branches; invol 2-3 mm, the invol bracts blunter and more oblong than in no. 40; rays 7-10(11), 1-2 mm; disk-fls 2-7; achenes short-hairy; 2n=18. Riverbanks from Pa., Md. and D.C. to Tenn., Ky., s. O., and s. Ind.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.