1 Leaves all simple, 4-12 cm wide, and also coarsely serrate (some of the lower leaves sometimes pinnately lacerate basally); rays 5, not lobed at the tip

1 Leaves simple, lobed, divided, or compound, but the margins of the leaves, leaflets or lobes entire, never serrate; rays (5-) 8 (-13).

  2 Rays entire (or with 1-2 obscure teeth at the tip); disc corollas 5-lobed; plants perennials; rays yellow; leaves strictly opposite

  2 Rays with 3-5 lobes or teeth at the tip; disc corollas 4- or 5-lobed; plants annuals or perennials; rays yellow (sometimes with a red or brown blaze at base), pink, purple, or white; leaves opposite, alternate, or both together.

    3 Disk flowers with 4 corolla lobes; disk flowers with 4 anthers.

      4 Leaves pinnately or bipinnately lobed into linear segments or narrowly lanceolate segments (sometimes plants with a mix of 1-pinnate and simple leaves as in C. leavenworthii); cypselae either wingless or with conspicuous, entire wings; [section Calliopsis].

        5 Cauline leaves usually 1-pinnate or simple; rays yellow throughout (rarely with red-brown blotches); pappi of 2 subulate scales; [s. AL and s. GA s. through peninsular FL]

        5 Cauline leaves usually 1-2+ pinnate; rays with basal red-brown blotches; pappus lacking or of 1-2 scales; [either widespread or endemic to s. TX].

          6 Plants typically 30-100 cm tall, sparsely branched from the bases; cypselae with or without wings; pappi 0.1-0.2 mm long; [widespread]

          6 Plants typically 10-30 cm tall, usually branched from the bases; cypselae 2-3 mm long, bearing conspicuous wings; pappi 0.2-1 mm long; [s. TX and n. MX]

      4 Leaves simple or with 1-2 auriculate lobes at the base, but lacking linear or pinnate segments; [section Eublepharis].

             7 All of the major cauline leaves opposite (except in C. linifolia the lowermost few leaves may be alternate).

               8 Ray flowers pink to white colored; plants rhizomatous

               8 Ray flowers yellow; plants fibrous-rooted.

                 9 Leaf blades ovate (to elliptical), very gradually reduced upward, margins ciliolate, surfaces lacking tiny dark dots; achenes about 5 mm long; [se. SC south to Panhandle FL]

                 9 Leaf blades linear-oblanceolate to linear, rapidly reduced upward, margins glabrous, surfaces with numerous tiny dark dots (easiest to see on undersurface); achenes < 2.5 mm long; [se. VA south to ne. and Panhandle FL, west to e. TX]

             7 All of the major cauline leaves alternate.

                   10 Ray flowers yellow; leaves with an expanded blade.

                     11 Outer phyllaries deltoid and very short, less than 0.3× as long as the inner phyllaries; flowering late Sep-Jan; [endemic to FL]

                     11 Outer phyllaries lanceolate, 0.4-0.8× as long as the inner phyllaries; flowering early May-early Nov; [collectively widespread].

                       12 Basal/lower leaves (at least 4 nodes) absent at anthesis; mid-cauline leaves linear to linear-lanceolate, or broadly to narrowly elliptical; achene awns 0.2-1.0 mm long; flowering Sep-Oct; [swamp forests and streamside openings, fresh-tidal creek margins; or wet calcareous savannas]; [from se. NC south to n. FL].

                          13 Leaves 8-15+ cm long, 2-7 mm wide, the blades linear to linear-oblanceolate, 20-50× as long as wide; achene awns 0.2-0.4 mm long

                          13 Leaves 4-15 cm long, 10-45 mm wide, the blades broadly to narrowly elliptical, 5-15× as long as wide; achene awns 0.7-1.0 mm long

                       12 Basal/lower leaves present at anthesis; leaves rapidly reduced upward such that mid-cauline leaves are narrow or slender; achene awns 0.5-1.5 mm long; flowering early May-early Nov; [wet savannas, seepage slopes, pitcher-plant bogs, streamhead ecotones, pocosin ecotones]; [collectively more widespread].

                            14 Leaves (at least one major leaf per plant) with 1-few slender lobes near the base (rarely no lobed leaves present or at least readily visible); achene wing broad, > 3/4 the width of the achene body; achene awns averaging 0.5 mm; leaf texture firm but not thick and leathery; flowering early May-early Jul; [se. VA south to e. GA]

                            14 Leaves without basal lobes; achene wing narrow, < ½ the width of the achene body; achene awns averaging 1.5 mm long; leaf texture thick and leathery; flowering mid Aug-early Nov; [se. NC south to c. FL and west to s. MS; also rarely inland in GA, NC, SC, off the Coastal Plain]

    3 Disk flowers with 5 corolla lobes; disk flowers with 5 anthers.

                              15 All of the leaves simple or the plant with a mixture of simple leaves and leaves with 1-2 (-4) basal auricles or leaflets, these distinctly smaller than the terminal lobe or leaflet.

                                16 Stems with (5-) 6-12 nodes between the first node > 1 cm above the basal leaves and the first head.

                                  17 Phyllaries primarily 9-12 mm long; laminae of rays ca. 20-30 mm long; peduncles 12-25 (-40) cm long

                                  17 Phyllaries primarily 5-8 mm long; laminae of rays ca. 12-15 mm long; peduncles (7-) 12-15 cm long.

                                    18 Leaf blades (or terminal leaflets of compound leaves) narrowly oblanceolate, to 0.6 cm wide

                                    18 Leaf blades (or terminal leaflets of compound leaves) elliptical to oblanceolate, 0.6-4 cm wide.

                                       19 Leaf blades (or terminal leaflets of compound leaves) more or less broadly elliptical, ca. 1.5-4 cm wide, acute; stem (and often also the leaves) rather densely hairy (to glabrate)

                                       19 Leaf blades (or terminal leaflets of compound leaves) narrowly elliptical to oblanceolate, ca. 0.6-2 cm wide, acuminate; stem and leaves glabrous

                                16 Stems with 1-5 (-8) nodes between the first node > 1 cm above the basal leaves and the first head.

                                         20 Annual; rays yellow, with a red-brown or purple blaze or spotting near the base.

                                           21 Leaves extending >1/2 way up the stem; bracts subtending the phyllaries 6-9 (-12) mm long; disc corollas with apices red-brown to purplish; cypselae wingless

                                           21 Leaves extending <1/2 way up the stem; bracts subtending the phyllaries 4-6 (-8) mm long; disc corollas with apices yellow; cypselae winged.

                                             22 Inner phyllaries dorsally pubescent; stems typically glabrous (at least on mid-lower stems)

                                             22 Inner phyllaries dorsally glabrous; stems typically densely pubescent (sometimes sparsely so)

                                         20 Perennial (cormose or rhizomatous at base, and sometimes also stoloniferous); rays completely yellow, lacking a red-brown or purple blaze or spotting near the base.

                                               23 Plants spreading by elongate stolons; leaf blades (or terminal leaflets) 1-2.2× as long as wide

                                               23 Plants lacking stolons; leaf blades (or terminal leaflets) > 3× as long as wide (basal leaves sometimes broader).

                                                 24 Leaves oblanceolate, infolded, only very rarely with basal lobes, 15-30× as long as wide; leaf surfaces completely glabrous; [endemic to calcareous glades of Jackson County, FL]

                                                 24 Leaves oblanceolate, not notably infolded, the larger often with basal lobes; leaf surfaces shortly pubescent at least along the veins; [widespread in our area]

                              15 Most or all of the leaves deeply lobed or dissected into distinct leaflets or divisions, the leaflets or divisions 3-20 or more, if only 3, then the lateral leaflets nearly or fully as large and well-developed as the terminal.

                                                    25 Disk flowers reddish; ray flowers usually with a basal red mark; leaflets of mid-cauline leaves 1-15 mm wide and about 1-10× as long as wide

                                                      26 Terminal leaflets of mid-cauline leaves 5-15 mm wide, < 3× as long as wide; lower stems more uniformly to densely pubescent; [mainly sandy soils or in disturbed situations east of the Mississippi River]

                                                      26 Leaflets of mid-cauline leaves 1-3 mm wide, 3-8× as long as wide; lower stems typically glabrous to slightly pubescent; [mainly calcareous soils, in TX]

                                                    25 Disk flowers yellow; ray flowers yellow; leaflets of mid-cauline leaves 0.5-6 (-10) mm wide and > 10× as long as wide.

                                                        27 Achene wings fimbriate; [of granitic outcrops of the Piedmont of GA and AL; disjunct in Ozark glades]

                                                        27 Achene wings entire; [collectively more widespread].

                                                          28 Midstem and upper stem leaves with 1-3 segments; plants reclining; flowering late Jun-Jul; [of dolomite glades in c. AL]

                                                          28 Midstem and upper stem leaves with > 5 segments; plants erect; flowering May-late Jun; [of granite outcrops, sandy woods, and similar open disturbed areas; collectively more widespread].

                                                            29 Larger segments of midstem and upper stem leaves 0.5-1.5 mm wide

                                                            29 Larger segments of midstem and upper stem leaves 2-6 (-10) mm wide.

                                                              30 Pappus teeth 0.5-1 mm long; [endemic to e. TX and s. OK]

                                                              30 Pappus teeth ca. 0.2-0.3 mm long; [scattered from NC, SC, and GA westward to e. TX and e. OK]

1 Rays primarily pink or purple, not white-tinged (flowers viewed from above, adaxial surface of the rays).

  2 Receptacles epaleate; leaves pinnatisect; [waif, ne. US]

  2 Receptacles paleate; leaves simple or bladeless; [widespread natives]

    3 Leaves broad and conspicuous; ray florets purple; disc florets many (200+), the corollas pink, green, red, purple, or yellow colored; [plants of prairies and similar habitats]

1 Rays primarily white to white-tinged or yellow throughout (lamina of the ray with at least some white basally if not uniformly yellow).

      4 Disc florets functionally staminate (thus cypselae only forming from ray florets)

      4 Disc florets bisexual, fertile.

        5 Leaves entire or toothed, but not deeply pinnatisect; sometimes with smaller rounded lobes (Leucanthemum basal leaves can have deeper, round lobes); plants usually not aromatic.

          6 Stem internodes usually winged (at least proximally)

          6 Stems not winged.

             7 Leaves primarily basal, the cauline leaves absent or fewer and much reduced in size from basal leaves; abaxial surface of the ray laminae white or sometimes pink-tinged (on live plants) but lacking a prominent colored midstripe.

               8 Leaves strigose, the margins crenate-serrate; roots not red-tipped; abaxial surface of ray laminae often pink or purple tinged, flowers closing at night

               8 Leaves glabrous (or faces sparsely hairy), the margins entire or toothed; roots usually red-tipped; rays drying pinkish but abaxial surface not conspicuously pink tinged on live plants

             7 Plants with well-developed cauline leaves, the margins entire or sometimes toothed (usually entire in Aphanostephus, occasionally deeply lobed); abaxial surface of the ray lamina sometimes white, but often with a prominent purple or blue midstripe (except Leucanthemum, which merely dries pink)

                 9 Flowering heads smaller, arranged in corymbiform or paniculiform arrays; ray florets with diminuitive laminae (0.3-5.0 mm long), heads thus sometimes superficially appearing disciform (rays sometimes double in horticultural forms as in Achillea ptarmica)

                   10 Plants aromatic; leaves linear to narrowly lanceolate, the surfaces glabrous or sparsely hairy; pales more or less folded but lacking distal papillae; cypselae not shed along with subtending phyllary and disc florets; [tribe Anthemideae]

                   10 Plants not aromatic; leaves variously shaped, at least some usually lyrate or oblanceolate (not all linear), the surfaces hairy and gland-dotted (at least abaxially); pales distally pappilate or fimbriate; cypselae shed along with subtending phyllary and 2 disc florets each invested in a pale; [tribe Heliantheae]

                 9 Flowering heads larger, singular on scapes (if in 2's or 3's, these large and not in broad corymbiform arrays), rays prominent, the laminae usually > 10 mm long

                     11 Rays white abaxially (drying pinkish); receptacles broadly convex, not pitted; plants rhizomatous perennials; pappus absent; [tribe Anthemideae]

                     11 Rays white or with prominent blue or purple midstripe (sometimes present after drying); receptacles conic, pitted; plants tap-rooted annuals (except Astranthium riddellii); pappus absent, coroniform, or of scales; [tribe Astereae]

                       12 Phyllaries scarious margined; cypselae 4-angled and with 4-12 thick ribs, pappus absent, of scales or coroniform; ray florets closing distally at night

                       12 Phyllaries sometimes hyaline but not scarious margined; cypselae compressed, lacking prominent ribs (though sometimes glochidiate), pappus absent or short coroniform; ray florets not closing at night

        5 Leaves deeply lobed or pinnatisect, the ultimate segments linear or if rounded, the sinuses of the lobes nearly reaching the midrib (pinnatifid); plants typically aromatic (except Tripleurospermum and Parthenium); [tribe Anthemideae].

                          13 Receptacles paleate (chaffy or with apparent bracts), the pales sometimes distally fimbriate or papillate (Parthenium).

                            14 Stem internodes usually winged

                            14 Stems not winged.

                              15 Rays (the laminae) white with conspicuous yellow coloration at the bases

                              15 Rays primarily white to white-tinged (without strong yellow color at the base of the laminae) or yellow throughout (lamina of the ray with at least some white basally; if rays are white).

                                16 Flowering heads smaller, arranged in corymbiform or paniculiform arrays; ray florets with diminuitive laminae (0.3-5.0 mm long); ray and disc florets both white or white-ish.

                                  17 Plants usually aromatic; pales more or less folded but not distally fimbriate or papillate; cypselae not shed along with phyllary and disc florets; [tribe Anthemideae]

                                  17 Plants not aromatic (at least not conspicuously so); pales distally fimbriate or papillate; cypselae shed along with subtending phyllary and 2 disc florets each invested in a pale; [tribe Heliantheae]

                                16 Flowering heads larger, arranged mostly singular at the ends of scapes, not in broad corymbiform arrays (except Tripleurospermum, which has larger heads and prominent rays), ray laminae prominent; ray and disc florets differing in color (rays typically white; discs typically yellow).

                                    18 Plants annual, erect or decumbent, ill-scented or not; ultimate leaf margins dentate to lobed; cypsela ribs usually 9-10 (sometimes lacking); [widespread non-natives]

                                    18 Plants perennial and prostrate (mat-forming), aromatic; ultimate leaf margins entire; cypsela ribs weak; [waif, ne. US]

                          13 Receptacles epaleate (lacking chaff).

                                       19 Ultimate leaf lobes broad, ovate-shaped (not linear)

                                       19 Ultimate leaf lobes linear.

                                         20 Plants usually aromatic; maturing flowering heads with deflexed ray laminae; cypsela 5-ribbed, lacking apical resin sacs

                                         20 Plants not aromatic; ray laminae not deflexed; cypsela with 3 ribs and 1-5 abaxial-apical resin sacs