1 Mid and upper stem leaves > 8× as long as wide; phyllaries tipped with a small, white spine; rays white (to pale pink); involucre 2.5-4.5 (-5) mm high; disc flowers 6-12 (-20) per head; [section Ericoidi]

1 Mid and upper stem leaves 2-7× as long as wide; phyllaries not spine-tipped; rays purple, lavender, rose, blue (rarely nearly white); involucre > 5 mm high (except sometimes as short as 4 mm high in S. adnatum of s. GA and FL west to LA); disc flowers (6-) 11-110 per head.

  2 Stem leaves 0.1-1(-1.3)cm long, either ascending-appressed, appearing adnate to stem, or triangular and deflexed; [of the Coastal Plain]; [section Patentes, series Brachyphylli].

    3 Blades of mid-stem leaves ascending-appressed, basally decurrent; [of s. GA south to s. FL, west to se. LA]

    3 Blades of mid-stem leaves spreading, the apical portion then abruptly deflexed, basally clasping; [of e. NC to c. peninsular FL]

  2 Stem leaves mostly ≥1.5 cm long, spreading to erect-ascending; [collectively widespread].

      4 Midstem leaves <3cm long, bases rounded to cuneate (sometimes subclasping); leaves and bracts silvery-sericeous (glabrous in S. concolor var. devestitum); leaves held erect-ascending, lower often twisted by 90 degrees to bring edge in line with stem; plants not stipitate-glandular; [section Virgulus].

        5 Bracts large, leafy, concealing involucres; plants branched; inflorescences open, involucres mostly terminal or clustered at ends of branches; rays 13-36; cypselas glabrous.

          6 Phyllaries with lower (outer) surfaces glabrous to glabrate (rarely sparsely to densely sericeous), the margins ciliate with thick-based, spreading hairs 0.5-1.0 mm long (much longer than those of the surfaces); largest phyllaries with terminal, green, pubescent portion 2/3-3/4 as long as the total phyllary length (longer than the proximal, indurated, glabrate portion); middle phyllaries mostly > 8 mm long and > 2.5 mm wide, averaging 9 (-14) mm long × 3 (-5) mm wide; involucre 8-15 mm tall; [mostly of the West Gulf Coastal Plain, disjunct e. to VA and s. GA]

          6 Phyllaries densely sericeous, the vestiture of the margins similar to that of the surfaces; largest phyllaries with terminal, green, pubescent portion 1/4-1/3 (-1/2) as long as the total phyllary length (shorter than the proximal, indurated, glabrate portion); middle phyllaries mostly < 7 mm long and < 2 mm wide, averaging 6 mm long × 2 mm wide; involucre 7-11 mm tall; [mostly of the Great Plains, s. to ne. TX, nw. AR, and s. IL]

        5 Peduncle bracts abruptly reduced, appressed, not concealing involucres; inflorescences racemose, sometimes subsecund, stems sparingly branched or unbranched; rays 7-16; cypselas densely strigose.

             7 Phyllaries long-acuminate, spreading to recurved; phyllaries with woolly, tangled hairs; involucre 7-9 mm tall; [c. FL Panhandle]

             7 Phyllaries acute, appressed; phyllaries either with appressed, straight hairs (moderately to densely sericeous) or glabrous to sparsely pilose; involucre 5-7 mm high; [collectively widespread].

               8 Phyllaries and upper stem leaves moderately to densely sericeous (silky-pubescent); [widespread]

               8 Phyllaries and upper stem leaves glabrous or sparsely pilose; [of the Gulf Coastal Plain]

      4 Midstem leaves >3cm, bases strongly cordate- or auriculate-clasping or subclasping to cuneate; leaves and bracts scabrous, strigoso-scabrous, or hirtellous; main stem leaves spreading or lax, not twisted; plants stipitate-glandular in arrays (glands sparse in S. fontinale and S. estesii; sometimes absent in S. patens).

                 9 Mid-stem leaves cuneate, rounded, or subclasping; [section Grandiflori].

                   10 Phyllaries appressed; phyllary faces glabrous or glabrate, lacking stipitate glands (though there may be a few stipitate glands on the phyllary margins); heads 6-7.6 mm high.

                     11 Involucres 5.0-6.4 mm high; rays white; [of wet prairies in the Eastern Highland Rim of TN]

                   10 Phyllaries spreading, squarrose, or reflexed; phyllary faces moderately to densely stipitate-glandular (and also often pubescent or scabrous with non-stipitate hairs); heads (5-) 7-12 (-15) mm high; [of dry habitats, of mainly inland provinces, though extending to the Coastal Plain in e. VA, e. NC, and nc. SC].

                       12 Involucres 8.5-12 (-15) mm high; phyllaries scabrous and stipitate-glandular; lower stem leaves (often withered by flowering season) cordate-clasping; [of acidic habitats of the Coastal Plain and Piedmont of e. and c. VA south through e. and c. NC to nc. SC]

                       12 Involucres 4-9 mm high; phyllaries pubescent and stipitate-glandular; lower stem leaves cuneate, rounded, or subclasping; [of calcareous habitats, south to sc. VA, w. NC, nc. AL, n. MS]

                          13 Upper stems, leaves, bracts, and outer phyllaries lacking stipitate glands, inner phyllaries densely stipitate-glandular; involucres (5-)30-150+, 4-6mm high; [interserial hybrid]

                          13 Upper stems, leaves, bracts, and phyllaries usually stipitate-glandular (also hirtellous); involucres 1-30(-70), (5-) 7-9mm high

                 9 Mid-stem leaves clasping to auriculate-clasping.

                            14 Phyllaries with attenuate, loosely spreading tips; disc flowers 50-110; ray flowers (40-) 50-75 (-100); [section Polyliguli]

                            14 Phyllaries with obtuse to acute tips (the inner phyllaries sometimes acuminate, but not attenuate); disc flowers 15-50; ray flowers 9-24 (-30); [section Patentes, series Patentes]

                              15 Involucres 8-10 (-12) mm high; disc flowers 8-10 mm long, white with purplish lobes; heads 4-5 (-6) cm across (ray tip to ray tip), the rays 14-24 mm long; plants strongly rhizomatous, forming clonal colonies with the stems mostly scattered along the rhizome (new stems typically arising at least several cm from the old ones); achenes 2.5-4.0 mm long, pale gray-brown, the trichomes about 0.4 mm long and distributed on and between the ribs; anthers purplish; pollen white

                              15 Involucres 5.5-7.5 (-8.5) mm high (or to 12 mm high in S. patens var patentissimum, barely entering our area in w. KY and w. MS); disc flowers 5.5-8 mm long, either white with purplish lobes or bright yellow; heads 3-4 (-4.5) cm across (ray tip to ray tip), the rays 10-18 (-20) mm long; plants cespitose, generally with 1 or more stems arising from caudices (the new stems arising near the old); achenes 2.0-4.0 mm long, tan, gray, brown, dark-brown, or black, the trichomes various (see below); anthers purplish or yellow; pollen white or yellow.

                                16 Disc flowers white with purplish lobes; stem leaves 7.5-12.5 (-14) cm long, thin in texture, soft-pubescent, the venation apparent, rugose-veiny and wrinkled; anthers purplish; pollen white; achenes 2.5-4.0 mm long, the trichomes concentrated on the ribs, < 0.4 mm long, appressed; [primarily of the Mountains, less commonly the Piedmont, mostly in moist, shady to semi-sunny situations]

                                16 Disc flowers bright yellow; stem leaves (2-) 3-7 (-9) cm long, thick in texture, scabrous, the venation inconspicuous; anthers yellow; pollen yellow; achenes 2.0-3.5 mm long, the trichomes distributed on and between the ribs, mostly > 0.4 mm long, spreading; [collectively widespread in our area, mostly in dry, semi-sunny to sunny situations]

                                  17 Involucres broadly turbinate, mostly 8-12 mm long; phyllaries in 4-7 series (grading into bracts), more or less appressed, obtuse to acute, middle ones 1.2-1.7 mm wide (ovate to lanceolate), densely strigillose or sericeous-strigose; plants largely eglandular (except for sparse sessile glands on phyllaries), usually with leaves only ca. 2-3 cm long at mid-stem, developing many long stiff branches with abrupt further reduction in leaf size; [from w. KY and w. MS westward]

                                  17 Involucres campanulate or narrowly turbinate, mostly 5-7.5 mm long; phyllaries in 4-5 (-6) series, often somewhat squarrose, acute to acuminate, middle ones 0.7-1.2 mm wide (linear to lanceolate), densely strigillose to almost glabrous; plants glandular (mostly stipitate-) or largely eglandular, with varied leaf size and branching; [collectively widespread].

                                    18 Mid-stem leaves mostly 5-7 cm long, separated by internodes of (1-) 1.5-3 (-4) cm at their densest, usually spreading; plants usually 0.8-1.6 m tall; heads mostly 9-12 mm wide

                                    18 Mid-stem leaves mostly 3-5 cm long, separated by internodes of (0.5-) 1-2 (-3) cm at their densest, often adnate-ascending; plants usually 0.4-0.8 m tall; heads mostly 7-11 mm wide.

                                       19 Stems and leaves generally eglandular (except sometimes for scattered glands on distal branches), but with dense ascending eglandular hairs; plants usually dull greyish-green, not much darkening when dried; leaves usually with gradual or irregular reduction from base of stem to summit; mid-stem leaves with length/width (2-) 2.5-4 (-4.5), not forming a distinct overlapping cluster; bracts on proximal thirds of peduncles mostly 2-3 (-5) mm wide

                                       19 Stems and leaves with dense to sparse stipitate-glands, with or without eglandular hairs; plants somewhat bluish-waxy, often becoming blackish when dried; leaves abruptly reduced in size with each branching order; mid-stem leaves [directly below inflorescence] with length/width (1.5-) 2-2.5(-3), clustered and overlapping along 10-20 cm; bracts on proximal thirds of peduncles mostly 1-2 (-3) mm wide

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)

             7 Peduncle bracts mostly ascending (-appressed), sometimes spreading, oblong-linear to linear-subulate, acute.

               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)

                   10 Stems glabrate, scabrous-puberulent, or strigose with coarse hairs; inflorescence diffuse; rays 20-25

      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]

                     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