9. Solidago gigantea Aiton (late goldenrod, tall goldenrod)

S. gigantea var. leiophylla Fernald

S. gigantea var. serotina (Kuntze) Cronquist

Pl. 242 a, b; Map 998

Plants with branched, long-creeping rhizomes, often also thickened at the stem bases. Stems 1 to several, 50–200 cm long, erect or ascending, with several fine, longitudinal lines or grooves, glabrous below the inflorescence (sparse to moderate, short hairs sometimes present along the inflorescence branches), not shiny, usually somewhat glaucous. Leaves chiefly cauline, the largest leaves toward the midpoint of the stem, the basal leaves usually absent at flowering. Basal and lowermost stem leaves with the blade 6–15 cm long, 1–3 cm wide, mostly 4–8 times as long as wide, narrowly oblanceolate to elliptic-lanceolate or narrowly elliptic, not or only slightly thickened (occasionally slightly fleshy when young), angled or more commonly tapered gradually to a sessile or very short-petiolate base, angled or tapered to a sharply pointed tip, the margins sharply toothed and usually microscopically roughened, the surfaces glabrous or more commonly the undersurface sparsely hairy mainly along the main veins, with 3 main veins, the lateral pair often originating well above the leaf base, finer than the midvein, the veinlets usually easily observed, forming an irregular, dense network. Median and upper stem leaves 1–20 cm long, elliptic to lanceolate or narrowly lanceolate, sessile, the margins of the uppermost leaves often entire, otherwise similar to the lower stem leaves. Inflorescences open to more commonly relatively dense, narrow to broad, often large, pyramidal panicles, the longer branches and often also the tip arched or nodding, the heads oriented upward along the branches. Involucre 2.5–4.0 mm long, the bracts in 3–6 unequal series. Involucral bracts lanceolate to narrowly oblong and bluntly to sharply pointed at the appressed-ascending tip, the margin sparsely hairy, the outer surface glabrous, with an often poorly differentiated, green central region of varying width toward the tip, this tapered gradually to the midvein above or below the bract midpoint (the outer series often nearly entirely green), the midvein somewhat thickened and no additional veins present. Receptacle naked. Ray florets 8–17, the corollas 3.5–5.0 mm long, yellow. Disc florets 6–12, the corollas 3.0–3.5 mm long, the lobes 0.5–0.9 mm long, yellow. Pappus 2.0–2.5 mm long, some of the bristles slightly thickened toward the tip. Fruits 1.3–1.7 mm long, obovoid, sparsely and finely hairy. 2n=18, 36, 54. July–October.

Scattered nearly throughout the state (U.S.; Canada; introduced in Europe). Bottomland forests, mesic to less commonly dry upland forests, banks of streams and rivers, margins of ponds and lakes, fens, bases and ledges of bluffs, bottomland and upland prairies, and rarely glades; also pastures, margins of crop fields, railroads, roadsides, and open, disturbed areas.

A number of varieties and forms have been segregated from typical S. gigantea based on differences in leaf width and pubescence. Morton (1984) studied the morphology of the complex throughout its range and concluded that there is no practical way of grouping the complex patterns of variation within the species into recognizable infraspecific taxa. His treatment is followed here. Solidago gigantea is a relatively glabrous member of the widespread S. canadensis complex. For a discussion of stem galls in this and related species, see the treatment of S. altissima.