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Key to Solidago, Key I: Key to a diversity of goldenrods with basally disposed leaves and paniculiform inflorescences with heads secund on the branches
[subgenus Nemorales; and subgenus Pleiactila, sections Argutae, Venosae, Maritimae, and Unilaterales)]

Asteraceae

Solidago

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1 Basal and lower stem leaves petiolate with a cordate or subcordate blade and/or a cordate-clasping petiole; [subsection Argutae].
  2 Pappus > ½× as long as the disc corollas; rays 1-3
  2 Pappus < ¼× as long as the disc corollas; rays 3-6
1 Basal and lower stem leaves with cuneate leaf blades and petioles not cordate-clasping (though leaves may have petioles which sheath the stem).
    3 Blades of lower leaves ovate to elliptic to oblanceolate, their bases truncate, abruptly tapering, or gradually tapering to petiole; lower leaves including petioles mostly less than 4× as long as wide (sometimes longer in S. brachyphylla with densely puberulent leaf surfaces and stems, and in S. boottii and S. tarda with blades sharply serrate and heads lacking phyllary-like bracts interior to ray florets); [subsection Argutae].
      4 Leaves either definitely scabrous or moderately to densely soft-villous or puberulent.
        5 Leaves scabrous on the upper surface.
          6 Involucre (2.5-) avg. 3.9 (-6.5) mm high; basal and lower stem leaves 8-30 cm long, 4-10 cm wide, mostly 2-3× as long as wide; upper stem leaves few, somewhat reduced; disc florets averaging 11.8 per head; [Mountains, Interior Low Plateau, rarely Piedmont, and Coastal Plain only from DE northwards]
          6 Involucre (3.5-) avg. 6.1 (-8.8) mm high; basal and lower stem leaves 6-24 cm long, 2-6 cm wide, mostly 3-5× as long as wide; upper stem leaves many, strongly reduced; disc florets averaging 9.3 per head; [Coastal Plain and very rarely lower Piedmont and AL Mountains]
        5 Leaves moderately to densely soft-villous or puberulent.
             7 Leaves soft-villous; rays 7-12; flowering May-Jun; [Coastal Plain of e. NC and e. SC]
             7 Leaves puberulent; rays 0 (-2); flowering Sep-Nov; [SC (NC?) south to FL and AL]
               8 Inner phyllaries linear; leaves green (not glaucous)
               8 Inner phyllaries oblong; leaves glaucous
      4 Leaves either glabrous (or nearly so) or strigose or strigillose.
                 9 Plants with slender, stoloniferous rhizomes (in addition to the main, more deeply-seated rhizomes)
                   10 Upper stem leaves quickly reduced in size compared to the lower, ascending or appressed; basal and lower stem leaves elliptic to obovate (rarely ovate), acute or obtuse, with narrowly attenuate bases; [LA, TX, AR, and OK]
                   10 Upper stem leaves gradually reduced in size, ascending to spreading; basal and lower stem leaves mostly ovate, acute to acuminate, with truncate to obtuse bases; [NJ south to AL]
                 9 Plants lacking slender, stoloniferous rhizomes.
                     11 Phyllaries striate, with several nerves prominent; involucres 4.5-6 (-7) mm high
                     11 Phyllaries not striate, only the midvein prominent; involucres 2.5-5.6 mm high.
                       12 Basal leaves truncate at the base; leaves thick in texture
                       12 Basal leaves cuneate to rounded at the base; leaves of normal herbaceous texture.
                          13 Achenes glabrous
                          13 Achenes strigillose, at least toward the apex.
                            14 Leaves strigose or strigillose
                            14 Leaves glabrous
    3 Blades of lower leaves oblanceolate to narrowly ovate, gradually tapering to petiole; lower leaves including petioles mostly more than 4× as long as wide (sometimes shorter in S. juncea with at least a few phyllary-like bracts interior to ray florets).
                              15 Petiole bases of basal and lower stem leaves not clasping or sheathing the stem; [of mesic or dry habitats].
                                16 Stems obviously densely and loosely puberulent; [subsection Nemorales]
                                  17 Pappus bristles usually exceeding the length of the ray floret corolla tubes; basal and lower stem leaves narrowly oblanceolate to nearly linear; leaf margins entire or with minute teeth only near the tip; disc corolla lobes (0.6-) 0.8-1.5 mm long; achenes moderately hairy; [mainly western in our region]
                                  17 Pappus bristles usually not (or barely) exceeding the length of the ray floret corolla tubes; basal and lower stem leaves oblanceolate to narrowly obovate; leaf margins crenate-serrate through half or more of their length; disc corolla lobes 0.5-0.9 (-1.0) mm long; achenes sparsely hairy; [widespread in our region]
                                16 Stems glabrous or nearly so; [subsection Junceae].
                                    18 Rhizomes thin, elongated, creeping; stem leaves usually 3-nerved; [disjunct from west to glades and barrens]
                                    18 Rhizomes thick, short; stem leaves not 3-nerved; [collectively of various habitats].
                                       19 Rays 7-13; disc florets 8-12
                                       19 Rays 3-7; disc florets 5-9
                                         20 Upper stem leaves ascending to appressed, usually lacking axillary fascicles; [west of the Blue Ridge]
                                         20 Upper stem leaves spreading or reflexed, with axillary fascicles of reduced leaves; [east of the Blue Ridge]
                              15 Petiole bases of basal and lower stem leaves sheathing the stem; [seasonally saturated habitats]; [subsection Maritimae].
                                           21 Leaves somewhat fleshy, the stem leaves reduced but not very markedly so; inflorescence almost always with lower branches strongly recurved with secund heads; [usually of maritime or otherwise saline habitats, rarely in nontidal marshes or swamps].
                                             22 Involucres 3-4 mm high; rays 7-11; disc flowers ca. 10-16; leaf margins ciliolate; larger leaves < 3 cm wide; [MA south to FL, west to TX and beyond]
                                             22 Involucres 4-7 mm high; rays 12-17; disc flowers ca. 17-22; leaf margins not ciliolate; larger leaves > 3 cm wide; [VA northward]
                                           21 Leaves not fleshy (rarely so in S. stricta of near coastal situations), the stem leaves much reduced relative to the basal; inflorescence showing only relatively weak tendency to recurved branches with secund heads; [inland habitats, except rarely S. stricta].
                                               23 Ray flowers averaging 3; disc flowers averaging 8; heads 6-7 mm tall; [seepage over sloping rock on granitic domes, of sw. NC, nw. SC, and ne. GA]
                                               23 Ray flowers averaging 5; disc flowers averaging 6; heads 4-5 mm tall; [peaty bogs and fens, w. NC and e. TN northward].
                                                 24 Basal leaves 0.7-2.5 cm wide; stem leaves linear or lanceolate (the lower cauline leaves 0.7-3 cm wide); disc flowers 9-15; [PA and WV (?) northwards]
                                                 24 Basal leaves 3-8 cm wide; stem leaves oblong-lanceolate (the lower cauline leaves 3-8 cm wide); disc flowers 4-8; [scattered in NC and TN; less sparsely distributed northwards]