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Key to Symphyotrichum, Key G: perennial asters
[of subgenus Symphyotrichum, section Dumosi, subsections Divergentes and Dumosi]

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1 Disc corolla lobes ½ - ¾ of the length of the corolla limb (the flared portion above the narrow corolla tube); disc corolla lobes spreading to reflexed.
..2 Plants cespitose, with short, branched caudices or short-rhizomatous; abaxial leaf faces glabrous, midveins ± densely pilose (rarely glabrate); ray flowers 8-15 (-23); disc corollas white to cream turning pink to purplish, lobes strongly reflexed (lengths 1/2-3/4 corollas); [wide variety of habitats]
..2 Plants colonial, long-rhizomatous; abaxial leaf faces and midveins usually sparsely to densely strigose or strigillose, sometimes glabrous (var. glabratum); ray flowers (10-) 15-26; disc corollas cream to light yellow turning purple to brown, lobes spreading (lengths ca. 1/2 corollas); [bottomlands and other wetlands]
1 Disc corolla lobes < ½ the length of the corolla limb (the flared portion above the narrow corolla tube); disc corolla lobes usually erect.
....3 Peduncles long (at least some > 2 cm long), with numerous small, closely-spaced bracts mostly 1-4 mm long and much smaller than the leaves; plants mostly not strongly rhizomatous (sometimes with multiple stems from short-creeping rhizomes); plants mostly < 10 dm tall.
......4 Involucres 7-12 mm high; rays light blue to purple; mid-stem leaves without axillary fascicles; [C. and s. IL and MO south to AR and e. OK]
......4 Involucres (3-) 4.5-6.3 mm high; rays pale blue, pink, lavender, or white; mid-stem leaves usually with axillary fascicles; [collectively widespread]
........5 Peduncle bracts, at least lower and middle, mostly spreading or reflexed, oblong to linear-oblong, obtuse to subacute (rarely abruptly mucronate)
........5 Peduncle bracts mostly ascending (-appressed), sometimes spreading, oblong-linear to linear-subulate, acute.
..........6 Cauline leaves 3-7 cm long; branches few; peduncles long; rays 14-17 (-20)
..........6 Cauline leaves to 15 cm long; branches abundant; peduncles long, short, or absent; rays 13-25.
............ 7 Stems glabrate; branches not crowded; most peduncles long, their bracts short and of ± uniform length and shape
............ 7 Stems glabrate, puberulent, or strigose; branches crowded; most peduncles short to absent, their bracts not uniform, some long and narrow.
............ ..8 Stems sparsely and finely puberulent; inflorescence small and terminal; rays 13-16 (-20)
............ ..8 Stems glabrate, scabrous-puberulent, or strigose with coarse hairs; inflorescence diffuse; rays 20-25
....3 Peduncles short (mostly < 2 cm long), sparsely bracteate or with leaves rather than bracts in close proximity to the heads; plants strongly colonial from creeping rhizomes; plants mostly > 10 dm tall;
............ ....9 Involucres (2.5-) 3.5-4.5 (-5.5) mm high; rays mostly < 20, usually white (rarely pink); ray blades 3-8 mm long; plants 3-9 (-10) dm tall.
............ ......10 Heads densely crowded in spikelike racemes, the peduncles mostly < 7 mm long
............ ......10 Heads in loose racemes or scattered on branch ends, the peduncles mostly 10-20 mm long
............ ....9 Involucres 3-7 (-8) mm high; rays mostly > 16, white, pink, or violet; ray blades mostly 6-15 mm long; plants 3-15 (-20) dm tall.
............ ........11 Leaves thin, planar; peduncle bracts 1-3 (-5).
............ ..........12 Outer phyllaries > 2/3 the length of the inner ones; heads usually subtended by large foliaceous bracts
............ ..........12 Outer phyllaries 1/3-2/3 the length of the inner ones; heads not usually subtended by large foliaceous bracts.
............ ............ 13 Plants 1.5-6 dm tall; [n. NJ northwards]
............ ............ 13 Plants mostly 6-15 dm tall; [collectively widespread]
............ ............ ..14 Stems stout, moderately to densely short-woolly or tomentose from their bases upward; [s. IL northwards]
............ ............ ..14 Stems stout to slender, glabrous or at most hairy in lines at their bases; [collectively widespread].
............ ............ ....15 Heads congested on lateral branches of arrays; involucres 3-4 mm high; [PA, s. OH, n. KY, and AR northwards]
............ ............ ....15 Heads not congested or congested only distally on lateral branches of arrays; involucres 3.6-5.6 (-6) mm high, and mostly > 4 mm high; [collectively widespread].
............ ............ ......16 Leaves linear to oblanceolate, reduced in arrays; involucres 3.6-5 (-6) mm high; rays white to purplish
............ ............ ......16 Leaves broadly oblanceolate, not much reduced in arrays; involucres usually 4-5.6 mm; rays white
............ ........11 Leaves stiff, margins revolute; peduncle bracts 5-12 or more (except 1-3 in S. boreale).
............ ............ ........17 Ray blades (7) 10-15 (20) mm long, white or pale rose to lavender; peduncle bracts 1-3
............ ............ ........17 Ray blades 5-11 (-12) mm long, pale lilac to medium blue or medium purple; peduncle bracts 5-12 or more.
............ ............ ..........18 Leaf veinlets obscure, or if more conspicuous then the areoles obviously longer than broad.
............ ............ ............ 19 Leaves linear, usually none toothed; plants to 8 dm tall; [bogs, wet pine savannas, FL Panhandle and s. AL]
............ ............ ............ 19 Leaves narrowly lanceolate, serrate; plants to 15 dm tall; [wetland and upland habitats, NC to s. FL, west to s. AL]
............ ............ ..........18 Leaf veinlets conspicuously reticulate on the lower surface, the areoles nearly isodiametric.
............ ............ ............ ..20 Leaves rather thick, lanceolate to elliptic.
............ ............ ............ ....21 Leaves glabrous or nearly so above.
............ ............ ............ ......22 Stem spreading puberulent throughout; lower leaf surface moderately to densely spreading-puberulent; [MO, AR, and LA westward]
............ ............ ............ ......22 Stem puberulent in lines above; lower leaf surface subglabrous to sparsely scabrous-puberulent; [widespread west of the Appalachians]