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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 Mid and upper stem leaves mostly linear or linear-lanceolate, nearly parallel-sided or narrowed from near strongly auriculate-clasping base; ray blades (7-) 10-15 (-20) mm; stems and leaf faces glabrous
1 Mid and upper stem leaves elliptic to linear, cuneate or attenuate at base (auriculate-clasping but broader in S. rhiannon, rarely subclasping in other species); ray blades 3-11 (-13) mm; stems and leaf faces glabrous or pubescent.
  2 Plants annuals, from a taproot, glabrous; involucres narrowly turbinate or cylindro-turbinate (in bloom, broadened from peduncle to apex); inflorescence open and diffuse, bracts subulate, appressed-ascending, and inconspicuous; stem leaves attenuate with strongly sheathing petioles; [subgenus Astropolium]
  2 Plants perennials, rhizomatous or from branched caudices, usually pubescent at least in lines on stems or along leaf veins; involucres more or less campanulate (contracted above middle, less commonly cylindric); inflorescence various, bracts foliaceous (subulate in some forms of S. dumosum); stem leaves sheathing or not.
    3 Stem leaves (below arrays) oblanceolate-elliptic or oblong-lanceolate, auriculate-clasping; inflorescences open, sparsely bracteate (bracts mostly 1-3 per peduncle, foliaceous), leaves and bracts much reduced in arrays; plants 1.5-4 (-6) dm tall; [ultramafic outcrop barrens, Clay co., NC]; [subsection Symphyotrichum, series Punicei]
    3 Stem leaves various, not auriculate clasping; inflorescences leafy, often crowded, leaves and bracts gradually reduced (or bracts abruptly reduced, but 5-15+ per peduncle); plants (0.5-) 3-15 dm tall; [widespread in a variety of habitats]
      4 Peduncles long (usually many on plant > 2 cm long), with copious (5-15+) small, closely-spaced, oblong or linear-subulate bracts mostly 1-4 mm long, abruptly smaller than the stem and branch leaves; plants single or somewhat cespitose (rhizomes short); phyllary apices acute to obtuse, green zones broadened near apex (oblanceolate or diamond-shaped).
        5 Leaves and bracts thin, lax; bracts usually gradually reduced, lower linear-elliptic, upper acicular; involucres (2.5-) 3.5-4.5 (-5.5) mm, cylindric
        5 Leaves and bracts thick, firm; bracts abruptly reduced from stem leaves, oblong to linear-subulate; involucres (3-) 4.5-6.3 mm, cylindro-campanulate.
          6 Upper stems and array branches moderately to densely hirtellous; adaxial faces of upper stem and branch leaves strigoso-scabrous; phyllaries and bracts usually prominently mucronate; plants usually sparsely stipitate-glandular in arrays; [May Prairie, TN]; [subgenus Virgulus]
          6 Upper stems and array branches strigose, mostly in lines; adaxial faces of upper stem and branch leaves glabrous to scabrous; plants eglandular; [widespread].
             7 Peduncle bracts, at least lower and middle, mostly spreading or reflexed, oblong to linear-oblong, obtuse to subacute (rarely abruptly mucronate)
               8 Cauline leaves 3-7 cm long; branches few; peduncles long; rays 14-17 (-20)
               8 Cauline leaves to 15 cm long; branches abundant; peduncles long, short, or absent; rays 13-25.
                 9 Stems glabrate; branches not crowded; most peduncles long, their bracts short and of ± uniform length and shape
                 9 Stems glabrate, puberulent, or strigose; branches crowded; most peduncles short to absent, their bracts not uniform, some long and narrow.
                   10 Stems sparsely and finely puberulent; inflorescence small and terminal; rays 13-16 (-20)
      4 Peduncles short (< 2 cm long), bracts gradually reduced, foliaceous; plants strongly colonial from creeping rhizomes (except S. lateriflorum and S. tradescantii); phyllary apices various, acuminate with longer or less distinct green zones in many species.
                     11 Upper stems, array branches, and both faces of leaves strigoso-scabrous or hirtellous (short, stiff, spreading hairs), usually densely so; plants usually stipitate-glandular distally (on upper stems, array branches, and leaves); leaves and bracts firm, stiffly spreading, sessile.
                       12 Leaf venation conspicuously reticulate, forming isodiametric areoles; leaf margins revolute; plants 5-15dm, arrays typically densely pyramidal with numerous, dense, often subsecund branches; [widespread]
                       12 Leaf areoles elongate and indistinct; leaf margins not revolute; plants 3-9dm, arrays loosely paniculiform; [FL]; [subgenus Virgulus]
                     11 Stems glabrous to pilose or villous (tomentose in S. lanceolatum var. hirsuticaule), leaves and bracts scabrous to glabrous adaxially and glabrous or strigillose, pilose, or villous abaxially (soft or appressed hairs, mostly on veins); plants eglandular; leaves lax.
                          13 Leaf veinlets conspicuously reticulate, forming isodiametric areoles visible on the lower surface; leaves waxy on upper surface (at least when young), the margins usually revolute and entire or weakly toothed; peduncle bracts 5-12 on well-developed peduncles, foliaceous, crowded, closely subtending and often partially obscuring involucres; ray flowers lavender or purple.
                              15 Stem puberulent in lines above; lower leaf surface subglabrous to sparsely scabrous-puberulent; [widespread west of the Appalachians]
                              15 Stem spreading puberulent throughout; lower leaf surface moderately to densely spreading-puberulent; [MO, AR, and LA westward]
                          13 Leaf veinlets indistinct or forming irregular, elongate areoles; leaves not waxy, margins plane or revolute; peduncle bracts, if 5 or more, gradually reduced and grading into phyllaries; ray flowers usually white (except S. simmondsii, S. kralii, and S. hesperium).
                                  17 Leaves thick, firm, margins recurved; involucres (4.5-) 6-8 mm; rays usually pale lavender or lilac; [coastal plain, NC south to FL and AL].
                                    18 Leaves linear, usually none toothed; plants to 8 dm tall; [bogs, wet pine savannas, FL Panhandle and s. AL]
                                    18 Leaves narrowly lanceolate, serrate; plants to 15 dm tall; [wetland and upland habitats, NC to s. FL, west to s. AL]
                                  17 Leaves thin, margins planar or (S. racemosum, S. eulae) recurved; involucres 3-5.6 (-6) mm (-7.2 mm in S. hesperium); rays usually white, sometimes pinkish-tinged (commonly purplish-blue in S. hesperium); [collectively widespread].
                                       19 Disc corolla lobes > 1/2 the length of the corolla limb, recurved; ray laminae (3-) 3.5-5.5 (-8) mm; rays 8-15 (-23).
                                         20 Disc corolla lobes cream (fading purplish), lobes to ¾ length of limb; rays mostly 8-15; plants cespitose; abaxial leaf faces glabrous (midveins ±pilose)
                                         20 Disc corolla lobes usually bright yellow (fading reddish-brown), lobes ca. 1/2 length of limb; rays mostly 16-26 (also keyed below); plants long-rhizomatous; abaxial leaf faces and midveins usually sparsely to densely strigose or strigillose
                                       19 Disc corolla lobes < 1/2 the length of the corolla limb, erect to spreading; ray laminae (4.2-) 5-10 (-14)mm; rays 16-45 (occasionally as few as 12 in S. racemosum and S. tradescantii).
                                           21 Plants short-rhizomatous and cespitose; leaf blades mostly < 1 cm wide, usually held erect-ascending; stems 1.5-6 dm tall, 1-3 mm wide at base; [rocky shores and river shoals, n. NJ northwards].
                                           21 Plants long-rhizomatous and colonial; leaf blades to 3 cm wide, lax or spreading; stems (3-) 6-15 dm tall, 3-6+ mm wide at base; [collectively widespread].
                                             22 Bracts grading into phyllaries, 5-12 on the longer peduncles (1-5 in S. ontarionis, with disc corolla lobes spreading and ca. 1/2 length of corolla limbs); leaf margins often revolute, serrate or less commonly entire; lower stem leaves usually petiolate.
                                               23 Disc corolla lobes mostly widely spreading, about 1/2 length of limbs, usually yellow (fading brownish); ray blades mostly 3.5-5.5 mm; leaves pubescent across face abaxially
                                               23 Disc corolla lobes mostly erect, < 1/2 length limbs, cream-colored or yellow (fading purple or brownish); ray blades > 5 mm; leaves glabrous or (S. racemosum) pilosulous on veins abaxially.
                                                 24 Involucres (4-) 5-6.5 mm; rays mostly (20-) 27-36, blades 8-11 mm; disc corollas yellow (fading brownish); [TX]
                                                 24 Involucres (2.5-) 3.5-4.5 (-5.5) mm; rays mostly (12-)16-20, blades 5-8 mm; disc corollas cream-colored (fading purplish); [widespread].
                                             22 Bracts foliaceous, not grading into phyllaries, 1-3 (-5) (disc corolla lobes < 1/2 length corolla limbs, erect to somewhat spreading); leaf margins flat, entire or with a few remote teeth; stem leaves sessile, slightly decurrent, often not much reduced upward (arrays leafy).
                                                      26 Outer phyllaries 1/3-2/3 the length of the inner ones; heads not usually subtended by large foliaceous bracts.
                                                        27 Stems stout to slender, glabrous or at most hairy in lines at their bases; [collectively widespread].
                                                          28 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].
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