1 Leaves primarily cauline, the basal leaves absent or withering early (if present, smaller than the lower and middle stem leaves), with the lower part of the stem usually naked or nearly so by the time of flowering.

..2 Heads borne in cylindrical and thyrsoid arrays, the central axis being the upper stem, the lateral branches of the array of similar length to one another and subtended by either well-developed leaves (longer than the branch) or smaller bracts (shorter than the branch).

....3 Leaves entire or obscurely few-toothed; achenes glabrous at maturity; outer phyllaries with squarrose tips (tips appressed in S. rigidiuscula); [subgenus Solidago, section Thyrsiflorae and section Erecta (in small part)].

....3 Leaves generally many- and sharp-toothed; achenes persistently pubescent; outer phyllaries with appressed tips; [subgenus Pleiactila; section Glomeruliflorae].

..2 Heads borne in paniculiform arrays (with longer lateral branches towards the middle or the base of the array, the heads on at least the longer branches secund).

......4 Leaves with only the midvein readily apparent; leaves entire; leaf surfaces finely translucent punctate (most obviously seen with transmitted light or with 10× magnification); fresh leaves usually anise-scented; [subgenus Triactis, section Odorae].

......4 Leaves either triple-veined or pinnately-veined; leaves entire or often at least obscurely toothed; leaf surfaces not translucent punctate; fresh leaves not anise-scented.

........5 Leaves triple-veined (two side veins arising near the base of the leaf and arching first away from and then back towards the midvein); leaves 2-20× as long as wide; [subgenus Pleiactila, section Unilaterales].

1 Leaves basally disposed, the basal leaves usually the longest leaves on the plant, often longer-petioled than the stem leaves, the stem leaves often graduating smaller upwards on the stem, though sometimes nearly even in size from lower stem to upper stem leaves.

..........6 Heads borne in corymbiform arrays, flat-topped or broadly rounded; array of heads about as broad as long, or broader.

............ 7 Larger leaves obovate, 5-10 cm long, 1.5-4 cm wide, with prominent teeth; plants small, 0.5-4 dm tall; [high elevation rock outcrops on Grandfather Mountain, Roan Mountain, and Hanging Rock Mountain (Avery, Watauga, and Mitchell counties, NC, and Carter County, TN)]; [subgenus Pleiactila, section Multiradiatae]

............ 7 Larger leaves elliptic-oblong, linear, or lanceolate, 6-25 cm long, 0.1-10 cm wide, with small, obscure teeth; plants more robust, 4-15 dm tall; [of low elevations]; [subgenus Pleiactila, section Ptarmicoidei]

..........6 Heads either borne in 1-several thyrsiform (cylindrical) arrays (the heads on short lateral axes about even in length from top to bottom of the array, the heads not secund), or in paniculiform arrays (with longer lateral branches towards the middle or the base of the array, the heads on at least the longer branches secund); array of heads usually much or at least somewhat longer than broad.

............ ..8 Petioles of the lower stem leaves sheathing the stem (appressed to it and curving around one side of it); leaves basally disposed, the leaves up the stem very many in most species, ascending or appressed, sometimes fewer and more widely spaced; inflorescence either narrowly cylindrical or with well-developed branches with heads secundly arrayed; plants of permanently or seasonally saturated wetlands (bogs, fens, seeps, wet pinelands, marsh edges), or of maritime habitats, or less typically of xerohydric acid flatwoods; [subgenus Pleiactila, section Maritimae].

............ ..8 Petioles of the lower stem leaves sessile (not sheathing, but auriculate-clasping at a ca. 90 degree angle to the stem in S. auriculata); leaves basally disposed, the leaves up the stem not very many and with short internodes in most species; inflorescence cylindric or paniculiform; plants of uplands, bottomlands, and sometimes seasonally saturated wetlands (bogs and fens).

............ ....9 Heads borne in paniculiform arrays (with longer lateral branches towards the middle or the base of the array, the heads on at least the longer branches secund)

............ ....9 Heads borne in a cylindrical and thyrsoid array, the central axis being the upper stem, the lateral branches of the array of similar length to one another and subtended by either well-developed leaves (longer than the branch) or smaller bracts (shorter than the branch).

............ ......10 Basal and lower stem leaves with blades truncate to cordate to a winged petiole; heads discoid (lacking ray flowers); [GA and FL Panhandle west through AL and MS to w. LA]; [subgenus Solidago, section Brintonia]

............ ......10 Basal and lower stem leaves sessile, or with blades cuneate to the petiole; heads radiate (with 1-16 disc flowers); [collectively widespread].

............ ........11 Heads very large, involucre 8-13 mm high; fresh leaves noticeably thick and rubbery in texture; [subgenus Pleiactila; subsection Glomeruliflorae]; [high elevations of NC and TN]

............ ........11 Heads smaller, involucre < 8 mm high (or 6-12 mm high in Solidago arenicola); fresh leaves not thick or rubbery in texture; [collectively widespread].

............ ..........12 Phyllaries and often also vegetative parts with minute sticky glands (use at least 10× magnification); stem leaves petiolate.

............ ..........12 Phyllaries and vegetative parts lacking minute sticky glands; stem leaves sessile.

............ ............ 13 Phyllaries squarrose; [subgenus Solidago, section Squarrosae]

............ ............ 13 Phyllaries appressed.

............ ............ ..14 Phyllaries stipitate-glandular (use 10× magnification); [outer Coastal Plain of se. NC]; [subgenus Solidago, section Villosicarpae]

............ ............ ..14 Phyllaries not glandular; [collectively widespread].