Solidago gigantea Aiton

Late Goldenrod, Tall Goldenrod

© SRTurner

Family - Asteraceae/Astereae

Habit - Perennial forb with branched, long-creeping rhizomes, often also thickened at the stem bases.

Stem - Ascending to erect, to 2 m, single or multiple from base, 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.

	Stem and nodes.
© SRTurner

Leaves - Alternate, simple. 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, angled or 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 (the undersurface often 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.

	Plant base. Basal leaves wilted at flowering, with best-developed leaves near midpoint of stem.
© SRTurner

	Stem and leaves.
© SRTurner

	Leaf adaxial.
© SRTurner

	Leaf adaxial surface.
© SRTurner

	Leaf abaxial.
© SRTurner

	Leaf abaxial surface.
© SRTurner

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.

	Inflorescence.
© SRTurner

	Inflorescence branch.
© SRTurner

	Inflorescence branch.
© SRTurner

Heads - 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.

	Involucres.
© SRTurner

Florets - Ray florets 8-17, pistillate, the corollas 3.5-5.0 mm long, yellow. Disc florets 6-12, perfect, the corollas 3.0-3.5 mm long, the lobes 0.5-0.9 mm long, yellow. Pappus of the ray and disc florets similar, of finely barbed bristles 2.0-2.5 mm long, some of the bristles slightly thickened toward the tip.

	Heads at anthesis, with exserted styles.
© SRTurner

Fruits - Achenes 1.3-1.7 mm long, obovoid, sparsely and finely hairy.

Flowering - July - October.

Habitat - Bottomland and mesic forests, streambanks, pond margins, fens, bluffs, prairies, pastures, crop field margins, railroads, roadsides, and open, disturbed areas.

Origin - Native to the U.S.

Lookalikes - Other goldenrods, particularly S. altissima.

Other info. - This species of goldenrod is found across Missouri, and is common across the eastern 2/3 of the continental U.S. and into Canada. Though common, it is slightly more conservative than S. altissima, which it somewhat resembles, and definitely prefers moister, shadier spots. It is easily differentiated from that species by the texture of its leaves, which are quite smooth in contrast to the rough feel of S. altissima leaves. The leaves have 3 main veins, most easily observed on the leaf underside, and the largest leaves are toward the middle of the stem.

Although the species has been subdivided into infraspecific phases, the pattern of character variation is complex and arguably not useful.

Photographs taken along the Riverfront Park, Washington, Franklin County, MO, 9-1-2024 (SRTurner).