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Key to Symphyotrichum, Key D: perennial asters [of subgenus Virgulus]

Asteraceae

Symphyotrichum

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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]
                     11 Involucres 6.0-7.6 mm high; rays pale pink, bluish, or violet; [of wet pinelands and marshes of e. Panhandle FL south to s. FL]
                   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]
                            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

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 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.
                              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].
                                         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 (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).
                                                        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].