1 Pappus present, of 5-60 barbellate bristles; receptacle naked (without paleae or well-developed bristles); [tribe Heliantheae; subtribe Eupatoriae].

  2 Plant a twining herb, phyllaries and disk florets 4 per head

  2 Plant stiffly erect to sprawling but never twining, phyllaries and disk florets usually > 4 per head.

    3 Leaves in whorls of 3-7, > 2 cm wide

    3 Leaves opposite, rarely alternate or whorled, if whorled, < 2 cm wide.

      4 Cypselae rostrate (with long beaks); the achene portion not bearing ribs

      4 Cypselae not beaked, the achene variously ribbed.

        5 Achenes (and ovaries) 8-10-ribbed; outer phyllaries longitudinally striate

        5 Achenes (and ovaries) (3-) 4-5-ribbed; outer phyllaries not noticeably longitudinally striate.

          6 Heads pink to blue.

             7 Phyllaries in 4-6+ series, deciduous

             7 Phyllaries in 2-4 series, persistent (or deciduous in Praxelis).

               8 Heads pink (rarely bluish); receptacles flat; florets 18-25 per head; leaves sometimes gland-dotted

               8 Heads blue; receptacles conic; florets 25-70 per head; leaves gland-dotted.

                 9 Bristles ca. 30; florets 35-70+; phyllaries ca. 25, subequal, persistent

                 9 Bristles ca. 40; florets 25-30; phyllaries 15-25, unequal, deciduous (absence apparent in fruit)

          6 Heads white to cream or, rarely, pale lilac.

                   10 Florets 3-7 per head

                   10 Florets at least 9 per head.

                     11 Phyllaries not strongly imbricate, with the principal ones subequal and sub-biseriate; petioles 0.5-10 cm

                     11 Phyllaries clearly imbricate, in 3+ series, the margins usually glandular; some species epetiolate

1 Pappus either absent, or of scales, setae, or awns; receptacle naked, paleate, or bearing bristles.

                       12 Leaves whorled, linear, < 2 mm wide; head solitary; [aquatic herb growing in shallow stagnant water]

                       12 Leaves opposite (or alternate in part), broader in shape and > 5 mm wide; heads typically not solitary; [terrestrial or wetland plants].

                          13 Receptacles naked (epaleate).

                            14 Pappus of 2-12 scales; heads white, pink, or blue (yellow in Schkuhria).

                              15 Heads with 20-125 florets; leaves serrate or ± dentate (at least distally); [rarely naturalized exotics or s. TX/FL natives]; [tribe Eupatorieae].

                                16 Leaves petiolate; corolla tube glabrous, typically blue or lavender colored (sometimes white tinged); heads with 20-125 florets; [naturalized exotics or s. FL native]

                                16 Leaves sessile; corolla tube glandular-pubescent, typically white colored (sometimes pink-purple tinged); heads with 75-125 florets; [s. TX native]

                              15 Heads with 10-30 florets (or fewer in Schkuhria); leaves entire; [natives, of FL, s. GA, MS, and TX in our area]; [tribe Heliantheae; subtribe Chaenactidinae].

                                  17 Leaves 3-5 lobed (or foliolate); cypselae with curled hairs (Florestina tripteris) or villous on angles (Schkuhria pinnata); [s. TX in our area or ne. waif].

                                    18 Heads discoid, corolla white; cypselae with curled hairs; [s. TX in our area]

                                    18 Heads discoid, sometimes with 1 (-2) diminuitive rays, corolla (of discs) yellow; cypselae villous, at least at bases or on angles; [waif of ne US, native in sw. US]

                                  17 Leaves simple or unlobed; cypselae with straight hairs; [variously distributed in s. GA and FL w. to MO and s. TX]

                            14 Pappus none, or of a few bristles or irregular coroniform lobes; heads green to yellow.

                                       19 Heads greenish or greenish yellow, borne in spiciform, racemiform, or paniculiform arrays.

                                         20 Heads in paniculiform arrays, all or most of the heads not subtended by bracts

                                         20 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract

                          13 Receptacles with paleae or well-developed bristles (the pales sometimes modified into specialized perigynia or burs surrounding the achene).

                                           21 Involucre of four decussate, deltoid bracts (the outer two large and longer than and often enclosing the flowering heads); pappus absent; paleae tightly enclosing the cypselae; plants rooting at the nodes, sometimes free-floating in water; [uncommon non-native, c. FL]

                                           21 Involucre not of four decussate, deltoid bracts; plants not with the above combination of characters; [widespread natives and non-natives]

                                             22 Heads small, less than 1 cm in diameter at anthesis (the female heads enlarging in Xanthium); disc florets dull white or suffused with green or purple; florets mainly unisexual (either in the same heads and then males central and females peripheral, or in separate female and male heads); female florets 0-8 per head; [tribe Heliantheae; subtribe Ambrosiinae].

                                               23 Heads unisexual; cypselas shed within an indurated bur or “nut” with hooked or straight spines developed from the phyllaries and/or paleae.

                                                 24 Involucre of the female heads with tubercles or straight spines developing from the phyllaries; burs 1-8 mm long

                                                 24 Involucre of the female heads with hooked spines developing from the phyllaries/paleae; burs 10-35 mm long

                                               23 Heads bisexual, with functionally male and female flowers in the same head; cypselas shed individually, not enclosed.

                                                    25 Heads in paniculiform arrays, all or most of the heads not subtended by bracts

                                                    25 Heads in spiciform or racemiform arrays, each 1 (-2) heads subtended by a bract

                                             22 Heads larger, mostly > 1 cm in diameter at anthesis; disc florets conspicuously white, yellow, pale yellow, or purple; florets mainly bisexual; female florets > 12 per head (except 2-8 in Polymnia and 8-15 in Verbesina occidentalis).

                                                      26 Leaves strongly basally disposed, the basal-most leaves sitting almost flat on the ground and overlapping; disc flowers maroon-purple

                                                      26 Leaves mainly or strictly cauline (not basally disposed); disc flowers white, yellow, or reddish-brown.

                                                        27 Disc flowers bright yellow or reddish-brown.

                                                          28 Involucre of phyllaries subtended by a calyculus of bracts obviously different in color, texture, and shape than the phyllaries.

                                                            29 Phyllaries usually distinct, rarely connate proximally; disk florets bright yellow

                                                            29 Phyllaries connate (both proximally-distally connate); disk florets yellow to reddish-brown

                                                          28 Involucre of phyllaries not subtended by a calyculus (phyllaries sometimes in 2+ series, but without obvious calyculi below).

                                                              30 Plants erect; heads without ray florets; [wet pine savannas and bogs; FL panhandle]

                                                              30 Plants primarily prostrate or trailing, sometimes erect; heads with or without ray florets; [habitats various, widespread natives and non-natives]

                                                        27 Disc flowers bright white or pale yellow.

                                                                 31 Stems not winged; plants erect or spreading.

                                                                   32 Cypselae 3-4 angled; pappus falling (of 2-12 awns or bristles); leaf margins irregularly crenate to serrate, the surfaces sometimes roughened but lacking glands; [e. of TX]

                                                                   32 Cypselae 5-ribbed; pappus absent; leaf margins entire or serrulate, the surfaces gland-dotted; [s. TX]

                                                                 31 Stems winged; plants erect.

                                                                     33 Disc flowers bright white; leaves unlobed or with 2 basal lobes

                                                                     33 Disc flowers creamy or pale yellow; leaves prominently pinnately lobed, with 5-many lobes

1 Ray florets white, pink, or purple (rarely pale yellow or lavender).

  2 Ray floret (the lamina) persistent on the achene and becoming papery and bleached

  2 Ray floret (the lamina) articulate from the achene and falling, thus the mature heads not appearing papery.

    3 Pappus of a minute crown (coroniform); disc florets white or whitish.

    3 Pappus not only coroniform, either absent or variously composed of scales, awns, or plumose bristles (Galinsogeopsis has 2 antrorsely barbed bristles plus a crowns of laciniate scales); disk florets yellow, red-brown, or pinkish.

      4 Heads with an involucre not subtended by a calyculus.

        5 Rays pink, the laminae 5-14 mm long; [OK and TX westward; subtribe Cheaenactidinae]

        5 Rays white or whitish-yellow; the laminae shorter, typically < 5 mm long (occasionally longer in Polymnia).

          6 Plants larger, 50-150+ cm tall; perennials; leaves > 10 cm long, sometimes with winged petioles or clasping basal appendages; disc florets functionally staminate; [natives of higher-quality, limestone or novaculite habitats; subtribe Polymniinae]

          6 Plants smaller, 2-40 cm tall or long (if stems > 40 cm then plants usually procumbent or decumbent); annuals or perennials; leaves usually < 10 cm long, lacking winged petioles or clasping basal appendages; disc florets bisexual and fertile.

             7 Stems usually copiously glandular-pubescent; leaf blades cordate to subdeltate or usually strongly 3-lobed (but not pinnate), the margins singly or doubly crenate; disc florets 40-100+; plants erect to decumbent; [native, s. TX westward; subtribe Peritylinae]

             7 Stems not copiously glandular-pubescent; leaf blades lanceolate to broadly ovate or deltate, or pinnately to palmately lobed (Tridax); plants erect or ascending to procumbent (Tridax]; [non-natives of disturbed habitats, widespread; subtribe Galinsoginae].

               8 Plants with leaves simple, unlobed; pappus either absent or of 5-20 laciniate or fimbriate scales; plants annual, erect

               8 Plants usually with a mix of simple and 3-lobed leaves; pappus usually of ca. 20 plumose (or setiform) scales; plants perennial, usually at least somewhat procumbent

      4 Heads with an involucre subtended by a calyculus of bracts (these often but not always reflexed); the phyllaries often appearing somewhat translucent or of a distinctly different color, shape, or texture from the leafy colored bracts below; [tribe Heliantheae; subtribe Coreopsidinae].

                 9 Phyllaries connate for at least ¼ their length; heads with or without ray florets; [MS westwards in our area]

                 9 Phyllaries distinct; heads with ray florets; [collectively widespread in our area].

                   10 Cypselas beaked, not strongly flattened, 7-30 mm long, with 1 groove per face; leaves highly dissected

                   10 Cypselas beakless, more or less strongly flattened and also often winged, 1.2-16 mm long, with 0 or 2 grooves per face; leaves simple to highly dissected.

                     11 Cypselas 2.5-16 mm long, usually not winged; pappus awns (if present) usually retrorsely barbed; rays white

                     11 Cypselas 1.2-4 mm long, winged (C. nudata) or not (C. rosea); pappus awns (if present) barbless; rays pink, purple, or white

1 Rays predominantly yellow, orange, or red (sometimes with some brown, maroon, or purple coloration as well).

                       12 Receptacle naked, epaleate.

                          13 Leaves and phyllaries with large, scattered, embedded oil glands, making the plants strongly aromatic (the glands translucent in living plants, usually golden-brown or blackish in herbarium specimens); plants annual, decumbent and much branched from the base (except Tagetes, annual and generally erect and sparingly branched); [tribe Heliantheae; subtribe Pectidinae].

                            14 Leaves unlobed, entire or serrate.

                              15 Leaves coarsely toothed, mostly opposite (the distal alternate)

                              15 Leaves entire (though with marginal setae), opposite

                            14 Leaves pinnately lobed or pinnatisect (pinnately divided nearly to the midrib but the leaflets not separate), the margins of terminal segments usually serrate (sometimes entire).

                                16 Pinnate leaf segments lanceolate, 3-10 mm wide; calyculus absent

                                16 Pinnate leaf segments linear, 1-3 mm wide; calyculus present, of linear bracts and subtending the involucre.

                                  17 Phyllaries distinct to their bases, or nearly so; ray florets 5-8; heads borne singly or in pairs/triplets; leaf surfaces puberulent

                                  17 Phyllaries connate > ½ their length; ray florets 5-21; heads borne singly; leaf surfaces glabrous to variously pubescent/floccose

                          13 Leaves and phyllaries lacking embedded oil glands, though smaller punctate glands sometimes present; perennial or annual plants, upright and little or moderately branched below the inflorescence.

                                    18 Leaf surfaces densely scabrous and canescent; [s. TX westward]

                                    18 Leaf surfaces glabrous to hirsute but never canescent; [collectively widespread]

                                       19 Leaves mainly basal or basally disposed (a few pairs low on the stem), the blades elliptic to ovate, the surfaces hirsute and stipate-glandular

                                       19 Leaves mainly cauline, the blades primarily linear, lanceolate oblanceolate, or occasionally oblong (if ovate, then leaves mostly cauline), the surfaces glabrous to strigose but not stipitate-glandular

                                         20 Pappus absent or of 1-2 antrorsely-barbed or subplumose bristles; leaf blades usually lobed; [c. and TX westward; formerly Perityle]

                                         20 Pappus absent, of scales, or coroniform (if coroniform then with 6-8 barbellulate bristles as in Jamesianthus); leaf blades unlobed; collectively widespread, including c. TX]

                                           21 Heads larger and fewer (< 9 per inflorescence), arranged singly or in loose corymbs; ray florets 6-14, the laminae conspicuous; phyllaries 12-18, broadly ovate, squarrose and in several imbricate series; [on calcareous substrates in n. AL and wc. GA]

                       12 Receptacle paleate, with paleae, bristles, or scales.

                                             22 Disc florets functionally staminate (“sterile”, not producing cypselae), the style undivided, their ovaries much smaller than ovaries of the ray florets (which are functionally pistillate).

                                               23 Inner phyllaries prickly with straight or uncinate prickles, and each enveloping a cypsela and swelling into a bur-like structure

                                               23 Inner phyllaries unarmed, not becoming bur-like (though those of Melampodium do invest the fruit).

                                                 24 Plants with tack-glands or pit-glands on stems, leaves, and/or phyllaries; [waif, e. TX; native further westward]

                                                 24 Plants without tack-glands or pit glands.

                                                    25 Outer phyllaries orbicular, connate 1/4 - 1/3 of their lengths; [exotic, rare]

                                                    25 Outer phyllaries orbicular to lance-linear, not connate; [native, collectively widespread in our area].

                                                      26 Phyllaries in 2 series; pappus coroniform (Chrysogonum) or absent (Lindheimera)

                                                        27 Plants perennial, often trailing; pappus persistent, forming a minute, half-cup-shaped crown; [e. LA eastward, e. of MS river]

                                                        27 Plants annual, erect; pappus absent (cypselae with 2 pappus-like processes originating from cypsela wings); [w. LA westward, w. of MS river]

                                                      26 Taller, robust plants, the stems usually 5-40 cm long at maturity, erect; pappus absent or of 2 awns.

                                                          28 Cypselae strongly flattened, borne in 2-3 series from the 2-3 series of ray florets

                                                          28 Cypselae thick, not flattened, borne in 1 series from the 1 series of ray florets

                                             22 Disc florets functionally bisexual (“fertile”, producing cypselae), the style divided, their ovaries as large as, or larger than, ovaries of the ray florets (which may be either functionally pistillate or completely neuter).

                                                            29 Ray corolla (the lamina) persistent on the achene and becoming papery and bleached.

                                                              30 Outer phyllaries with a stiff, maroon-colored subulate apex

                                                              30 Outer phyllaries lacking a stiff subulate apex.

                                                                 31 Leaf margins serrate or toothed; plant a perennial; cypselae subterete, 4-5 mm long; [natives]

                                                                 31 Leaf margins entire; plant an annual; cypselae 3-angled or flattened, 6-10 mm long; [non-native waifs]

                                                            29 Ray corolla articulate from the achene and falling after flowering.

                                                                   32 Pappus of 20 plumose bristles 4-5 (-7.5) mm long

                                                                   32 Pappus absent or of scales or awns (if with awnlike bristles as in Acmella, then these never plumose).

                                                                     33 Plants with tack-glands or pit-glands on stems, leaves, and/or phyllaries; [waif, VA and NC northward; subtribe Madiinae]

                                                                     33 Plants without tack-glands or pit-glands on stems, leaves, and/or phyllaries; [natives and non-natives, collectively widespread]

                                                                       34 Paleae not notably clasping the cypsela; cypselae notably flattened (or weakly compressed/angled in Guizotia); heads small, the receptacle 3-8 mm in diameter (ca. 10-15 mm in Guizotia).

                                                                         35 Pappus absent; ray laminae longer, 8-14 mm long

                                                                         35 Pappus persistent, of 2-3(-5) scales or awns; ray laminae shorter, 2-5 mm long.

                                                                           36 Cypselae of two types, strongly dimorphic: those of the rays smooth and flattened, the margins conspicuously lacerate and the pappus awns reduced in length; those of the discs ribbed and muricate, with 2 lengthened and divergent awns

                                                                           36 Cypselae of the rays and discs similar, monomorphic and not as above (the achenes weakly dimorphic in C. vialis, but the apical awns of similar length and the margins with only small, inconspicuous winglike projections)

                                                                       34 Paleae either entirely enveloping and falling with each cypsela or conduplicate (V-shaped in cross section), the 2 sides of the V partially clasping the cypsela; cypselae flattened, terete, or angled; heads mostly larger.

                                                                              37 Phyllaries apparently 4, the outer 4 foliaceous and forming a fused quadrangle which conceals the much smaller and narrower inner phyllaries (each inner phyllary subtending a ray floret); cypselae finely 32-40 ribbed

                                                                              37 Phyllaries not as above, instead 5 or more and not forming a conspicuously fused quandrangle; cypselae angled or smooth (sometimes angled, but lacking many fine ribs)

                                                                                38 Paleae completely surrounding the cypselae of the disc florets, forming a perigynium or sac-like appendage

                                                                                38 Paleae conduplicate or partially enclosing the cypselae, but not forming a sac-like appendage.

                                                                                  39 Disc florets with hairy staminal filaments; pappus of 4-6 aristate to lacerate scales; [TX westward]

                                                                                  39 Disc florets without hairy staminal filaments; pappus absent or of 2-3 scales or awns (sometimes accompanied by up to 8-12 additional shorter scales in Helianthus and Simsia, but these readily falling); [collectively widespread].

                                                                                    40 Rays primarily orange; [waif of FL, AL, and LA]

                                                                                    40 Rays primarily yellow; [natives and non-natives, collectively widespread]

                                                                                      41 Cypselae (of at least the disc florets) strongly flattened and generally also winged (thin-margined in Simsia).

                                                                                        42 Cypselae 3-7 mm long; erect herbs; stems often winged

                                                                                        42 Cypselae 1-2.5 mm (Acmella) or 3.5-6 mm long (Simsia); plants erect, decumbent, or prostrate; stems never winged.

                                                                                           43 Phyllaries 8-15; cypselae 1-2.5 mm long; involucre ca. 3-6 mm in diameter

                                                                                           43 Phyllaries 13-43; cypselae 3.5-6 mm long; involucre 5-16+ mm in diameter

                                                                                      41 Cypselae subterete, quadrangular, variously angled, or diamond-shaped in ×-section, not winged.

                                                                                             44 Ray florets pistillate (“fertile”).

                                                                                               45 Erect herb; leaves entire or with a few teeth; peduncles < 3 cm long

                                                                                               45 Creeping herb; leaves serrate and also mostly 3-lobed; peduncles 3-10 cm long

                                                                                             44 Ray florets completely neuter.

                                                                                                 46 Leaves linear; plants perennial with woody caudices; pappus absent; leaf surfaces and ray laminae abaxially gland-dotted; [SC waif; native to sw. US]

                                                                                                 46 Leaf blades usually broader (if linear, leaves either whorled or pappus present); plants annual or perennial, with or without woody caudices; pappus typically of scales or awns; [collectively widespread in our flora area].

                                                                                                   47 Leaves linear, lanceolate, or ovate, almost always some leaves on a plant > 7 mm wide; plants from crowns, some species with thickened vertical storage roots (only H. tuberosus producing horizontal tubers); [collectively widespread in our area]

                                                                                                   47 Leaves linear, 0.5-7 mm wide; plants from slender horizontal tubers; [c. FL north to s. AL]