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Key to Asteraceae, Key C: herbaceous composites with opposite leaves and radiate heads

Asteraceae

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1 Ray floret 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 floret white or whitish.
    3 Pappus not only coroniform, either absent or variously composed of scale, awn, or plumose bristle (Galinsogeopsis has 2 antrorsely barbed bristle plus a crown of laciniate scale); disk floret yellow, red-brown, or pinkish.
      4 Heads with an involucre not subtended by a calyculus.
        5 Ray pink, the laminae 5-14 mm long; [OK and TX westward; subtribe Cheaenactidinae]
        5 Ray 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 petiole or clasping basal appendage; disc floret 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 petiole or clasping basal appendage; disc floret bisexual and fertile.
             7 Stems usually copiously glandular-pubescent; leaf blade cordate to subdeltate or usually strongly 3-lobed (but not pinnate), the margin singly or doubly crenate; disc floret 40-100+; plants erect to decumbent; [native, s. TX westward; subtribe Peritylinae]
             7 Stems not copiously glandular-pubescent; leaf blade 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 scale; plants annual, erect
               8 Plants usually with a mix of simple and 3-lobed leaves; pappus usually of ca. 20 plumose (or setiform) scale; plants perennial, usually at least somewhat procumbent
      4 Heads with an involucre subtended by a calyculus of bract (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 bract below; [tribe Heliantheae; subtribe Coreopsidinae].
                 9 Phyllaries connate for at least ¼ their length; heads with or without ray floret; [MS westwards in our area]
                 9 Phyllaries distinct; heads with ray floret; [collectively widespread in our area].
                   10 Cypsela beaked, not strongly flattened, 7-30 mm long, with 1 groove per face; leaves highly dissected
                   10 Cypsela 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 Cypsela 2.5-16 mm long, usually not winged; pappus awn (if present) usually retrorsely barbed; ray white
                     11 Cypsela 1.2-4 mm long, winged (C. nudata) or not (C. rosea); pappus awn (if present) barbless; ray pink, purple, or white
1 Ray 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 gland, making the plants strongly aromatic (the gland 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 leaflet not separate), the margin of terminal segment usually serrate (sometimes entire).
                                16 Pinnate leaf segment lanceolate, 3-10 mm wide; calyculus absent
                                16 Pinnate leaf segment linear, 1-3 mm wide; calyculus present, of linear bract and subtending the involucre.
                                  17 Phyllaries distinct to their base, or nearly so; ray floret 5-8; heads borne singly or in pairs/triplets; leaf surfaces puberulent
                                  17 Phyllaries connate > ½ their length; ray floret 5-21; heads borne singly; leaf surfaces glabrous to variously pubescent/floccose
                          13 Leaves and phyllaries lacking embedded oil gland, though smaller punctate gland 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 blade elliptic to ovate, the surfaces hirsute and stipate-glandular
                                       19 Leaves mainly cauline, the blade 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 bristle; leaf blade usually lobed; [c. and TX westward; formerly Perityle]
                                         20 Pappus absent, of scale, or coroniform (if coroniform then with 6-8 barbellulate bristle as in Jamesianthus); leaf blade unlobed; collectively widespread, including c. TX]
                                           21 Heads smaller and many (10-300+), arranged into dense, flat-topped corymb; disc floret 1-15; ray floret 0-2, the laminae inconspicuous; phyllaries 6 (-9), in 1 series; [collectively more widespread but absent from n. AL and wc. GA]
                                           21 Heads larger and fewer (< 9 per inflorescence), arranged singly or in loose corymb; ray floret 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, bristle, or scale.
                                             22 Disc floret functionally staminate (“sterile”, not producing cypselae), the style undivided, their ovaries much smaller than ovaries of the ray floret (which are functionally pistillate).
                                               23 Inner phyllaries prickly with straight or uncinate prickle, 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-gland or pit-gland on stems, leaves, and/or phyllaries; [waif, e. TX; native further westward]
                                                 24 Plants without tack-gland or pit gland.
                                                    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 process 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 awn.
                                                          28 Cypselae thick, not flattened, borne in 1 series from the 1 series of ray floret
                                             22 Disc floret functionally bisexual (“fertile”, producing cypselae), the style divided, their ovaries as large as, or larger than, ovaries of the ray floret (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 margin serrate or toothed; plant a perennial; cypselae subterete, 4-5 mm long; [natives]
                                                                 31 Leaf margin entire; plant an annual; cypselae 3-angled or flattened, 6-10 mm long; [non-native waif]
                                                            29 Ray corolla articulate from the achene and falling after flowering.
                                                                   32 Pappus of 20 plumose bristle 4-5 (-7.5) mm long
                                                                   32 Pappus absent or of scale or awn (if with awnlike bristle as in Acmella, then these never plumose).
                                                                     33 Plants with tack-gland or pit-gland on stems, leaves, and/or phyllaries; [waif, VA and NC northward; subtribe Madiinae]
                                                                     33 Plants without tack-gland or pit-gland 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) scale or awn; ray laminae shorter, 2-5 mm long.
                                                                           36 Cypselae of two types, strongly dimorphic: those of the ray smooth and flattened, the margin conspicuously lacerate and the pappus awn reduced in length; those of the disc ribbed and muricate, with 2 lengthened and divergent awn
                                                                           36 Cypselae of the ray and disc similar, monomorphic and not as above (the achene weakly dimorphic in C. vialis, but the apical awn of similar length and the margin 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 rib)
                                                                                38 Paleae completely surrounding the cypselae of the disc floret, forming a perigynium or sac-like appendage
                                                                                38 Paleae conduplicate or partially enclosing the cypselae, but not forming a sac-like appendage.
                                                                                  39 Disc floret with hairy staminal filament; pappus of 4-6 aristate to lacerate scale; [TX westward]
                                                                                  39 Disc floret without hairy staminal filament; pappus absent or of 2-3 scale or awn (sometimes accompanied by up to 8-12 additional shorter scale in Helianthus and Simsia, but these readily falling); [collectively widespread].
                                                                                    40 Ray primarily orange; [waif of FL, AL, and LA]
                                                                                    40 Ray primarily yellow; [natives and non-natives, collectively widespread]
                                                                                      41 Cypselae (of at least the disc floret) 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 floret pistillate (“fertile”).
                                                                                               45 Erect herb; leaves entire or with a few teeth; peduncle < 3 cm long
                                                                                               45 Creeping herb; leaves serrate and also mostly 3-lobed; peduncle 3-10 cm long
                                                                                             44 Ray floret 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 blade usually broader (if linear, leaves either whorled or pappus present); plants annual or perennial, with or without woody caudices; pappus typically of scale or awn; [collectively widespread in our flora area].
                                                                                                   47 Leaves linear, lanceolate, or ovate, almost always some leaves on a plant > 7 mm wide; plants from crown, some species with thickened vertical storage root (only H. tuberosus producing horizontal tuber); [collectively widespread in our area]
                                                                                                   47 Leaves linear, 0.5-7 mm wide; plants from slender horizontal tuber; [c. FL north to s. AL]

Key to Asteraceae, Key J: Herbaceous composites with the leaves alternate or basal and the heads radiate, the rays yellow, orange, red

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1 Disc floret functionally staminate (sterile), with style undivided.
  2 Phyllaries 10 or less, in 2 series; plants annual; [primarily OK and TX]
  2 Phyllaries 12 or more, in (2-) 3-4 series; plants perennial; [collectively widespread, including OK and TX in our area]
    3 Cypselae with broad wings with 2 confluent awn
    3 Cypselae not winged, pappus absent or of 2-4 ciliate scale.
      4 Disc floret green, red, or maroon; pappus absent; leaves lanceolate, lyrate, or lyrate-pinnatifid (but not deeply pinnatifid); [nc. TX westward]
      4 Disc floret primarily yellow; pappus of 2-4 ciliate scale; leaves deeply pinnatifid [sw. AR and e. TX westward, waif in e. LA]
1 Disc floret bisexual (fertile), with style bifurcate.
        5 Leaves decurrent down the stem (the stem appearing winged); cypselae strongly flattened and often winged
        5 Leaves not decurrent; cypselae moderately compressed to 4-angled, not winged (or if winged, the cypselae obcompressed or obconic).
          6 Receptacular bract connate to form a honeycomb-like structure in which the flowers are set; pappus of 7-12 scale
          6 Receptacular bract not fused and not forming a honeycomb-like structure; pappus absent, of awn/scale, or a fused crown (Phoebanthus sometimes with up to 4 additional scale shorter than 2 primary lacerate scale).
             7 Heads subtended by a calyculus (bract distinct from phyllaries)
             7 Heads without a calyculus.
               8 Leaves conspicuously clasping the stem
               8 Leaves not noticeably clasping the stem.
                 9 Leaves pinnately lobed, the primary lobe usually pectinately divided; [non-native]
                 9 Leaves unlobed or if pinnatifid to pinnately lobed, the primary lobe not pectinate; [natives].
                   10 Pappus of 2 caducous, or readily-falling scale; receptacle flat
                   10 Pappus absent, or of 1-2 lacerate scale (on shoulders of cypselae) plus additional lacerate (bristlelike) scale; receptacle subspheric, conical, columnar, or otherwise convex.
                     11 Receptacle low conic to convex; phyllaries (14-) 20-40+, in 2-3 series.
                       12 Leaf blade linear; plants from slender, horizontal tuber; pappus absent or of 1-2 lacerate scale (on shoulders of cypselae) plus additional lacerate (bristlelike) scale; [natives of AL and FL; subtribe Ecliptinae]
                       12 Leaf blade variously shaped, not all linear (often with some ovate or rhombic leaves); plants from woody caudices; pappus absent; [waif in SC, native in arid southwest; subtribe Helianthinae]
                     11 Receptacle strongly conic or columnar; phyllaries 3-21, in 1-2 series; [subtribe Rudbeckiinae].
                          13 Phyllary series unequal (outer longer than inner); cypselae strongly compressed; ray floret subtended by receptacular bract
                          13 Phyllary series subequal; cypselae not strongly compressed; ray floret not subtended by receptacular bract (only the disc flowers with bract)

Key to Asteraceae, Key L: Herbaceous composites with the leaves alternate or basal and the heads radiate, the rays white, pink, purple, and the 0 pappus

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1 Ray primarily pink or purple, not white-tinged (flowers viewed from above, adaxial surface of the ray).
  2 Receptacle epaleate; leaves pinnatisect; [waif, ne. US]
  2 Receptacle paleate; leaves simple or bladeless; [widespread natives]
    3 Leaves without blade (the petiole terete, appearing Juncus-like); ray floret pink or purplish; disc floret fewer (60-120+), the corolla usually yellowish; [wet pinelands and seepages]
    3 Leaves broad and conspicuous; ray floret purple; disc floret many (200+), the corolla pink, green, red, purple, or yellow colored; [plants of prairie and similar habitats]
1 Ray primarily white to white-tinged or yellow throughout (lamina of the ray with at least some white basally if not uniformly yellow).
      4 Disc floret functionally staminate (thus cypselae only forming from ray floret)
      4 Disc floret bisexual, fertile.
        5 Leaves entire or toothed, but not deeply pinnatisect; sometimes with smaller rounded lobe (Leucanthemum basal leaves can have deeper, round lobe); plants usually not aromatic.
          6 Stem internode 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 margin crenate-serrate; root 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 margin entire or toothed; root usually red-tipped; ray drying pinkish but abaxial surface not conspicuously pink tinged on live plants
             7 Plants with well-developed cauline leaves, the margin 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 floret with diminuitive laminae (0.3-5.0 mm long), heads thus sometimes superficially appearing disciform (ray 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 floret; [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 floret each invested in a pale; [tribe Heliantheae]
                 9 Flowering heads larger, singular on scape (if in 2's or 3's, these large and not in broad corymbiform arrays), ray prominent, the laminae usually > 10 mm long
                     11 Ray white abaxially (drying pinkish); receptacle broadly convex, not pitted; plants rhizomatous perennials; pappus absent; [tribe Anthemideae]
                     11 Ray white or with prominent blue or purple midstripe (sometimes present after drying); receptacle conic, pitted; plants tap-rooted annuals (except Astranthium riddellii); pappus absent, coroniform, or of scale; [tribe Astereae]
                       12 Phyllaries scarious margined; cypselae 4-angled and with 4-12 thick rib, pappus absent, of scale or coroniform; ray floret closing distally at night
                       12 Phyllaries sometimes hyaline but not scarious margined; cypselae compressed, lacking prominent rib (though sometimes glochidiate), pappus absent or short coroniform; ray floret not closing at night
        5 Leaves deeply lobed or pinnatisect, the ultimate segment linear or if rounded, the sinus of the lobe nearly reaching the midrib (pinnatifid); plants typically aromatic (except Tripleurospermum and Parthenium); [tribe Anthemideae].
                          13 Receptacle paleate (chaffy or with apparent bract), the pales sometimes distally fimbriate or papillate (Parthenium).
                            14 Stem internode usually winged
                            14 Stems not winged.
                              15 Ray (the laminae) white with conspicuous yellow coloration at the base
                              15 Ray 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 ray are white).
                                16 Flowering heads smaller, arranged in corymbiform or paniculiform arrays; ray floret with diminuitive laminae (0.3-5.0 mm long); ray and disc floret 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 floret; [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 floret each invested in a pale; [tribe Heliantheae]
                                16 Flowering heads larger, arranged mostly singular at the ends of scape, not in broad corymbiform arrays (except Tripleurospermum, which has larger heads and prominent ray), ray laminae prominent; ray and disc floret differing in color (ray typically white; disc typically yellow).
                                    18 Plants annual, erect or decumbent, ill-scented or not; ultimate leaf margin dentate to lobed; cypsela rib usually 9-10 (sometimes lacking); [widespread non-natives]
                                    18 Plants perennial and prostrate (mat-forming), aromatic; ultimate leaf margin entire; cypsela rib weak; [waif, ne. US]
                          13 Receptacle epaleate (lacking chaff).
                                       19 Ultimate leaf lobe broad, ovate-shaped (not linear)
                                       19 Ultimate leaf lobe linear.
                                         20 Plants usually aromatic; maturing flowering heads with deflexed ray laminae; cypsela 5-ribbed, lacking apical resin sac
                                         20 Plants not aromatic; ray laminae not deflexed; cypsela with 3 rib and 1-5 abaxial-apical resin sac