1 Leaves with only the midvein readily apparent; leaves entire; leaf surfaces finely translucent punctate (most obviously seen with transmitted light or with 10× magnification); fresh leaves usually anise-scented; [subgenus Triactis, section Odorae].

..2 Main leaves ovate to lanceolate, 2-5 (-6)× as long as wide; stem pubescence general and circumferential; [of FL]

..2 Main leaves lanceolate to linear, (4-) 5-15× as long as wide; stem pubescence in lines decurrent down the stem from the margins of the leaf bases; [widespread]

1 Leaves either triple-veined or pinnately-veined; leaves entire or often at least obscurely toothed; leaf surfaces not translucent punctate; fresh leaves not anise-scented.

....3 Leaves pinnately veined; leaves mostly 3-5× as long as wide.

......4 Leaf venation not notably reticulate; plants to 12 dm tall, from a compact caudex; [subgenus Pleiactila, section Venosae, subsection Ulmifoliae].

........5 Leaves glabrous

........5 Leaves sparsely hirsute below, at least on the midvein and larger lateral veins

......4 Leaves pinnately veined and also forming a prominent reticulum, the veins (primary, secondary, and tertiary) very evidently raised on the undersurface (less obviously so in S. fistulosa); plants to 30 (-40) dm tall, from long-creeping rhizomes, thus forming clonal patches; [subgenus Pleiactila, section Venosae, subsection Venosae].

..........6 Mid-stem leaves sessile, somewhat clasping; leaf margins nearly entire to obscurely serrulate; leaves planar

..........6 Mid-stem leaves subsessile, not clasping; leaf margins strongly serrate; leaves rugose.

............ 7 Involucres 4-6 mm high; broader phyllaries 0.7-1.2 mm wide; stems glabrous below the inflorescence; mid-stem leaves elliptic (widest near the middle)

............ 7 Involucres (2-) 2.5-3.5 (4.5) mm high; phyllaries mostly < 0.5 mm wide; stems hairy or glabrous below the inflorescence; mid-stem leaves lanceolate to ovate (widest below the middle).

............ ..8 Leaves relatively thin, not very rugose, usually sharply serrate, the apices acuminate, glabrous or soft-hairy on the surfaces; rays (4-) 5-12 (-13).

............ ....9 Stem glabrous throughout (except for scattered hairs in inflorescence), stem with striate ridges decurrent from leaf bases; leaf blades appressed serrate (teeth short), blades glabrous beneath except for sparse, short, appressed, straight hairs; early blooming (1 month earlier than S. rugosa in same area); [permanently saturated, ± forested wetlands with Sphagnum moss, such as red maple-Atlantic white cedar swamps, streamhead pocosins, montane bogs]

............ ....9 Stem pubescent with crinkly hairs throughout (occasional plants varying to glabrate below), stem without striate ridges decurrent from leaf bases; leaf blades sharply serrate (teeth coarse), blades villous to crinkly hairy beneath; late blooming (ca. 1 month later than S. aestivalis in same area); [dry to moist fields, meadows, and other open habitats]

............ ..8 Leaves relatively thick and firm, strongly rugose, usually subentire to bluntly serrate, the apices often only acute, slightly to strongly scabrous or stiffly-hairy on the surfaces; rays 4-9.

............ ......10 Inflorescences narrow, the lower lateral branches only slightly exceeding the subtending leaves; leaves sparsely pubescent; [of the Southern Appalachians]

............ ......10 Inflorescences broad, the lower lateral branches generally much longer than the subtending leaves; leaves moderately to densely pubescent; [collectively widespread].

............ ........11 Upper stem leaves lanceolate to elliptic, not much reduced relative to leaves lower on the stem

............ ........11 Upper stem leaves ovate, much reduced relative to leaves lower on the stem

....3 Leaves triple-veined (two side veins arising near the base of the leaf and arching first away and then back towards the midvein); leaves 2-20× as long as wide.

............ ..........12 Upper stem (above the midpoint, up to the branches of the inflorescence) glabrous.

............ ............ 13 Plants to 20 dm tall; basal leaves never present; mid-stem leaves averaging 4-6× as long as wide; upper stem usually slightly to moderately glaucous as well as glabrous; [widespread]; [subgenus Pleiactilis, section Unilaterales, subsection Serotinae]

............ ............ 13 Plants to 10 dm tall; basal leaves withering or not before flowering (if not, also keyed elsewhere), often with assocated sterile offshoots with basal leaves; mid-stem leaves averaging 5-10× as long as wide; upper stem glabrous, green; [KY, TN, and MS westwards].

............ ............ ..14 Rootstock short and branched, not producing creeping rhizomes; ray flowers 5-8; receptacle lacking intercalated green bracts (resembling phyllaries) inward from the rays; mid and upper stem leaves usually lacking axillary fascicles of smaller leaves; [subgenus Pleiactilis, section Unilaterales, subsection Radulae]

............ ............ ..14 Rootstock producing creeping rhizomes; ray flowers 7-13; receptacle often with a few intercalated green bracts (resembling phyllaries) inward from the rays; mid and upper stem leaves usually with axillary fascicles of smaller leaves; [subgenus Pleiactilis, section Unilaterales, subsection Junceae]

............ ..........12 Upper stem hairy (above the midpoint, up to the branches of the inflorescence), variously puberulent, strigillose to strigose, villous, or scabrous.

............ ............ ....15 Midstem leaf blades 1-4 (-5)× as long as wide, the base attenuated to a winged petiole (at least in leaves of the lower midstem(; plants 1-10 dm tall; [collectively in IL, MO, AR, and LA westwards, disjunct eastwards in KY, NC, SC, GA, and AL]

............ ............ ......16 Leaf margins entire to finely serrate; midstem leaf blades mostly 2-4 (-5)× as long as wide; leaf surface vestiture appressed to scabrous; [subgenus Pleiactilis, section Unilaterales, subsection Radulae].

............ ............ ........17 Leaf surfaces with appressed (strigillose) hairs; upper stem vestiture densely strigose, the stems appearing grayish-green; rhizomes long-creeping, the plants forming clonal patches; [OK and nc. TX westwards and northwestwards]

............ ............ ........17 Leaf surfaces scabrous; upper stem vestiture scabrous to loosely puberulent, the stems appearing green or dingy green; rhizomes short (less commonly moderately creeping); [se. KS, OK, and TX eastwards]

............ ............ ....15 Midstem leaf blades 4-20× as long as wide, the base sessile and cuneate to rounded; plants 3-20 dm tall; [collectively widespread].

............ ............ ..........18 Rays 2-8; midstem leaves 4-15 mm wide, mostly 6-20× as long as wide, either twisted at base or not.

............ ............ ............ 19 Larger mid-stem leaves lanceolate to narrowly elliptic, 7-10 cm long, 10-15 mm wide; leaves not twisted; [KY and s. IN]; [subgenus Pleiactilis, section Unilaterales, subsection Canadensae]

............ ............ ............ 19 Larger mid-stem leaves linear to lance-linear, 2-9 cm wide, 2-7 (-10) mm wide; leaves either twisted at base or not; [either OK and westwards, or Coastal Plain from VA to FL west to TX and AR].

............ ............ ............ ..20 Leaves 4-9 cm long, 4-5 mm wide; [inland provinces, OK and westwards]; [subgenus Pleiactilis, section Unilaterales, subsection Radulae]

............ ............ ............ ..20 Leaves 2-7 cm long, 2-7 (-10) mm wide; [Coastal Plain, VA to FL west to TX and AR]; [subgenus Pleiactilis, section Unilaterales, subsection Tortifoliae]

............ ............ ..........18 Rays 4-17 (-24); midstem leaves 5-30 mm wide, 4-12× as long as wide, not twisted at base.

............ ............ ............ ....21 Midstem leaves mostly 8-12× as long as wide.

............ ............ ............ ......22 Rays 10-15; [wet pine savanna and marsh habitats, Coastal Plain of NC, SC, GA, FL, AL, and MS]; [subgenus Pleiactilis, section Unilaterales, subsection Tortifoliae]

............ ............ ............ ......22 Rays 7-11; [riverscour habitats, inland provinces of PA, MD, DC, VA, WV, IN, KY, TN]; [subgenus Pleiactilis, section Unilaterales, subsection Canadensae]

............ ............ ............ ....21 Midstem leaves mostly 4-6× as long as wide; [subgenus Pleiactilis, section Unilaterales, subsection Canadensae].

............ ............ ............ ........23 Mid-stem leaves serrate, the teeth 3-8 (-10) per side, the largest > 1.5 mm long; involucres 1.7-2.5 (-3.0) mm high.

............ ............ ............ ..........24 Lower to mid-stem glabrous or sparsely pubescent

............ ............ ............ ..........24 Lower to mid-stem moderately pubescent

............ ............ ............ ........23 Mid-stem leaves entire to serrulate, the teeth usually 0-6 per side (up to 14); involucres (2.5-) 3-4.5 mm high.

............ ............ ............ ............ 25 Upper surface of the leaves moderately to densely pubescent with short, curved to spreading hairs; [western]

............ ............ ............ ............ 25 Upper surface of the leaves sparsely to moderately roughened with minute bulbous-based hairs (stouter and shorter than the hairs on the lower surface), or glabrous except along the veins.

............ ............ ............ ............ ..26 Inflorescence broad; upper stem leaves not reduced in size relative to the mid-stem leaves; [broadly eastern]

............ ............ ............ ............ ..26 Inflorescence elongated, narrow; upper stem leaves reduced; [southern]