Plants 40-200 cm; caudices short, stout. Stems 1-10(-20+), erect or ascending, glabrous throughout or hairy in arrays. Leaves: rosettes present at flowering; basal and proximal cauline tapering to long, winged petioles sheathing stems or nearly so, blades narrowly ovate to oblanceolate, 100-400 × 10-60 mm, thick or fleshy, entire, acute, glabrous; mid to distal cauline usually numerous, sessile, blades lanceolate, 40-60 × 5-10 mm, reduced distally, thick or fleshy, bases sometimes subclasping, margins entire. Heads 20-500 , secund, in paniculiform arrays, secund-pyramidal to broadly club-shaped, sometimes leafy proximally, at least proximal branches spreading-recurved, branches and peduncles bracteolate, bracteoles reduced distally. Peduncles 2-3 mm, glabrous or sparsely hairy. Involucres 3-7 mm. Phyllaries in 3-4 series, unequal, lanceolate, margins ciliate, apices acute. Ray florets 8-17; laminae 5-6.2 × 0.4-0.6 mm. Disc florets 10-22; corollas 3-3.2 mm, lobes 0.5-1.2 mm. Cypselae (obconic) 1.1-1.5 mm, moderately strigose; pappi 3.8-4 mm (slightly clavate). Solidago sempervirens is common along the seacoast from the Gulf of St. Lawrence to central America and the northern West Indies. Introduced populations are sometimes very large near the Detroit River and Lake Erie in southwestern Ontario, eastern Michigan, and adjacent Ohio. A second disjunct group of populations occurs in Illinois and Indiana in the Chicago area at the southern end of Lake Michigan. Two mostly geographically separate subspecies can be recognized in the flora range. A race also occurs in the Azores and is undoubtedly introduced there [Solidago sempervirens var. azorica (Hochstetter ex Seubert) H. St. John]. Plants cultivated in European gardens have been labeled S. sempervirens var. viminea (Aiton) A. Gray.
Plants somewhat succulent, 4-20 dm, usually with a very short and compact caudex, essentially glabrous, or scabrous-puberulent in the infl; lvs ±basally disposed, entire, the largest ones oblanceolate, 10-40 נ1-6 cm, the cauline ones generally rather numerous; infl dense, paniculiform, sometimes leafy at base, at least the lower branches ±recurved-secund; invol 3-7 mm, its bracts acute or acuminate; rays 3-5 mm; achenes hairy; 2n=18, 36. Saline places along the coast from the Gulf of St. Lawrence to trop. Amer., and recently spreading inland locally, especially along highways that are salted in winter, even as far w. as e. Ill. Var. sempervirens, with relatively large heads (invol 4-7 mm, rays 12-17, disk- fls 17-22) is northern, s. to N.J. and locally to Va. Var. mexicana (L.) Fernald, with smaller heads (invol 3-4 mm or seldom 5 mm, rays 7-11, disk-fls 10-16), and commonly also with narrower lvs, is southern, rarely extending as far n. as Mass. Hybridizes with no. 36 as well as with no. 14 [Solidago stricta Aiton].
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.