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Key to Symphyotrichum, Key A: perennial asters with petiolate, cordate-bladed lower leaves
[of subgenus Symphyotrichum, sections Heterophylli and Concinni]

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1 Disc flowers 33-50 (or more); ray flowers (13-) 20-45; involucre 5-10 mm high; phyllary tips spreading to squarrose.
..2 Phyllaries linear, in 4-7 series; disc flowers 4.0-5.5 mm long; [IL and n. MO south through MO and se. KS to s. AR and se. OK]
..2 Phyllaries broadly lanceolate, foliaceous, in 3-4 (-5) series; disc flowers 5.8-6.8 mm long; [w. NC and e. TN south to nw. SC and n. GA]
1 Disc flowers (8-) 10-25 (-30); ray flowers 8-20 (-25); involucre 3.8-7 mm high (or to 8 mm high in S. oolentangiense); phyllary tips appressed (or the outer phyllaries loose or spreading).
....3 Cauline leaf blades sessile and cordate-clasping, or petiolate, the petiole strongly dilated to a cordate-clasping base, or both
....3 Cauline leaves not cordate clasping; [collectively widespread].
......4 Lower stems glabrous; upper stems sparsely hirtellous or pilose.
........5 Basal leaves deeply cordate; phyllaries with lanceolate diamond shaped blaze (2-3× as long as wide), purple to greenish purple
........5 Basal leaves shallowly cordate to truncate; phyllaries with short diamond shaped blaze (1-1.5× as long as wide) or linear-lanceolate-shaped blaze (> 4× as long as wide), green.
..........6 Phyllaries with linear-lanceolate-shaped green blaze (> 4× as long as wide)
..........6 Phyllaries with short diamond shaped green blaze (1-1.5× as long as wide)
............ 7 Plants solitary; [moist habitats, more widespread]
............ 7 Plants colonial by slender rhizomes; [shale in VA]
......4 Lower stems glabrous to sparsely hirsute; upper stems densely hirtellous to hirsute; [mainly west of the Appalachians].
............ ..8 Phyllaries with short diamond-shaped green blaze (1-1.5× as long as wide); basal and lower stem leaves mostly crenate to entire; upper stem leaves entire.
............ ....9 Plants with only the basal and lower stem leaf blades cordate or subcordate, the midstem and upper leaves not petiolate and with cuneate bases; phyllary faces glabrous; disc flowers (15-) 20-25 (-30)
............ ....9 Plants with nearly all basal and stem leaf blades cordate or subcordate; phyllary faces short-pubescent; disc flowers 16-23
............ ..8 Phyllaries with elongate green blaze (> 2× as long as wide); basal and lower stem leaves serrate or crenate; upper stem leaves serrate or crenate (to entire).
............ ......10 Plants 4-12 dm tall; cypselas glabrous
............ ......10 Plants 3-8 dm tall; cypselas strigillose