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 Upper stems and array branches moderately to densely hirtellous; adaxial faces of upper stem and branch leaves with dense short hairs (strigoso-scabrous); phyllaries and bracts usually prominently mucronate; plants usually sparsely stipitate-glandular in arrays; [May Prairie, TN]; [subgenus Virgulus]

        5 Upper stems and array branches glabrate, puberulent, or strigose; adaxial faces of upper stem and branch leaves glabrous to scabrous; plants eglandular; [collectively widespread].

          6 Peduncle bracts and array leaves spreading or reflexed, obtuse or abruptly mucronate; phyllaries tightly appressed, blazes rhombic.

             7 Rays 9-17 (-19); leaves (3-) 4-9 cm long; array leaves and bracts thick, firm, linear-oblong; [MD, PA, OH, KY, s. IL, se. MO, AR, and se. OK and southwards]

             7 Rays 19-26; leaves 3-5 cm long; array leaves and bracts thin-textured, oblong; [VA northwards]

          6 Peduncle bracts and array leaves ascending, tapered to acute apex; phyllary blazes often oblanceolate.

               8 Inflorescence diffuse, branches and peduncles long, wiry, divaricate; branch leaves and peduncle bracts subequal (within orders), all short, linear-subulate; [mainly Coastal Plain, from NC southwards and westwards]

               8 Inflorescence paniculiform, ±crowded, branches mostly erect-ascending and restricted to upper ½ of plant (broadly pyramidal with spreading-arching branches in S. racemosum var. subdumosum); branch leaves and peduncle bracts decreasing gradually in size, often broader; [collectively widespread].

                 9 Involucres cylindric, 3.5-4.5 mm high; cauline leaves (withered by flowering) mostly narrow-elliptic or lanceolate, 5-20 mm wide; arrays broadly pyramidal, leafy, branch leaves and bracts gradually reduced from stem leaves

                 9 Involucres cylindro-campanulate, (4-) 4.5-6.5 mm high; cauline leaves (often persistent), linear, 3-7 (-10) mm wide; arrays relatively narrowly paniculiform, branch leaves and bracts abruptly reduced from stem leaves.

                   10 Peduncles mostly exceeding array leaves; upper stems finely puberulent; leaves thin-textured; [mainly PA, OH, and MO northward]

                   10 Peduncles about equal to or shorter than subtending array leaves; upper stems glabrate or slightly scabrous; leaves firm, slightly fleshy; [outer Coastal Plain of NC and SC]

      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.

                            14 Leaves thin, linear to linear-lanceolate

                            14 Leaves rather thick, lanceolate to elliptic.

                              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]

                                16 Leaves harshly scabrous above

                                16 Leaves glabrous or nearly so above

                          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].

                                                    25 Heads densely crowded in spikelike racemes, the peduncles mostly < 7 mm long

                                                    25 Heads in loose racemes or scattered on branch ends, the peduncles mostly 10-20 mm long

                                             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 > 2/3 the length of the inner ones; heads usually subtended by large foliaceous bracts

                                                      26 Outer phyllaries 1/3-2/3 the length of the inner ones; heads not usually subtended by large foliaceous bracts.

                                                        27 Stems stout, moderately to densely short-woolly or tomentose from their bases upward; [s. IL northwards]

                                                        27 Stems stout to slender, glabrous or at most hairy in lines at their bases; [collectively widespread].

                                                          28 Heads congested on lateral branches of arrays; involucres 3-4 mm high; [PA, s. OH, n. KY, and AR northwards]

                                                          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].

                                                            29 Leaves linear to oblanceolate, reduced in arrays; involucres 3.6-5 (-6) mm high; rays white to purplish

                                                            29 Leaves broadly oblanceolate, not much reduced in arrays; involucres usually 4-5.6 mm; rays white