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

Asteraceae

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1 Pappus absent, or of crowns (coroniform) or scales (the scales entire, erose, aristate, or occasionally lacerate, but ultimately with broadened bases compared to bristles).
  2 Stems usually winged from decurrent leaf bases (except H. amarum, which bares stems with copious, mostly entire, linear leaves)
  2 Stems not winged.
    3 Pappus absent.
      4 Phyllaries in (3-) 4-9+ series, usually with apices hooked or looped; pappus of setiform awns or scales but falling (thus sometimes appearing absent post maturation)
      4 Phyllaries in 2-4 series, usually with apices not notably hooked or looped; pappus absent entirely (not just falling).
        5 Receptacles pitted and hairy (the hairs swollen and apically hooked); [primarily native in western portion of our area]
        5 Receptacles not pitted, nor hairy; [waifs].
          6 Leaves entire or sometimes toothed, but not pinnately lobed; receptacle epaleate or sometimes with short bristles or setae
             7 Heads smaller, the involucres (excluding phyllary apices) 0.8-7.5 mm in diameter.
               8 Ray floret laminae fan-shaped and apically 3 or 5 lobed (the laminae sometimes very short and not surpassing phyllary length in Hymenoxys).
                 9 Cauline leaves pronounced, simple or with 3-19+ lobes (the lobes linear-filiform); cypselae villous or pubescent (rarely glabrous); heads radiant, sometimes appearing nearly discoid due to diminutive or inconspicuous ray florets
                 9 Leaves strongly basally-disposed (except T. linearifolia, with basal and cauline leaves, the cauline leaves not with linear lobes), entire or with 2-6 teeth (or sometimes lobes); cypselae moderately to densely pubescent; heads clearly radiate
                   10 Leaves pinnately compound with linear leaf segments 1-3 mm wide (if not pinnate as in T. tephroleuca, then plants ashy white subshrubs); calyculus present (occasionally absent), of linear bracts subtending the involucre; plants with translucent oil glands evident throughout most parts; [subtribe Pectidinae]
                   10 Leaves simple (if also sometimes subshrubs, these not ashy white as in Gutierrezia); calyculus absent; plants sometimes gland-dotted on leaves (or sometimes also with resinous phyllaries, but not with oil glands throughout).
                     11 Plants annual, with a strong terpenoid smell when crushed, the leaves and phyllaries glutinous; phyllaries 12-15 in 1-2(-3) series
                     11 Plants annuals, biennials, or perennials, if annuals then not bearing a strong terpenoid smell when crushed, the leaves sometimes glutinous but not also the phyllaries; phyllaries 4-40 in 2-4 series (Gutierrezia) or 5-12 in 1-2 series (Psilostrophe).
                       12 Stems glabrous, or papillate-scabrous (but not clearly gray-green in appearance); involucre 1.5-5.5 mm in diameter; plants either annuals or subshrubs; phyllaries 4-40 in 2-4 series
                       12 Stems arachno-villous, appearing gray-green; involucre 4-7 mm in diameter; plants biennials or perennials; phyllaries 5-12 in 1-2 series
             7 Heads larger, the involucres (8-) 10-20+ mm in diameter.
                            14 Pappus in 1 series, of mostly 2-3 smooth to setiform awns OR subulate scales 2.5-8 mm long (sometimes with up to 6-8 total barbellulate/setiform awns in G. squarrosa, G. lanceolata, and G. texana)
                          13 Phyllaries in 2-3 series (2-3+ in Gaillardia); cypselae villous or otherwise sparsely to densely pubescent; leaves entire, toothed, or sometimes pinnately lobed (the lobes linear, as in Hymenoxys).
                              15 Receptacles entirely epaleate, not bearing any minute setae; ray florets (apical portion of the laminae) 3-5 lobed.
                                16 Cauline leaves pronounced, simple or with 3-19+ lobes (the lobes linear-filiform); cypselae villous or pubescent (rarely glabrous); heads radiant, sometimes appearing nearly discoid due to diminutive or inconspicuous ray florets
                                16 Leaves strongly basally-disposed (except T. linearifolia, with basal and cauline leaves, the cauline leaves not with linear lobes), entire or with 2-6 teeth (or sometimes lobes); cypselae moderately to densely pubescent; heads clearly radiate
                              15 Receptacles typically with spine-like setae or enations (except Gaillardia aestivalis) or very short bristles (i.e. not appearing "chaffy" overall, but these setae apparent upon dissection of the heads); ray florets (apical portion of the laminae) either unlobed (Amblyolepis) or 3-5 lobed (Gaillardia).
                                  17 Plants sweet-scented; cypselae prominently 10-ribbed; pappus scale apices rounded to acuminate but never aristate; heads borne singly or in paniculiform arrays; ray florets (the laminae) yellow; phyllaries usually not strongly reflexed in fruit
                                  17 Plants not sweet-scented; cypselae ca. 4-angled but lacking numerous prominent ribs; pappus scale apices often aristate; heads borne singly; ray florets (the laminae) often bicolored; phyllaries usually strongly reflexed in fruit
1 Pappus of barbellate to barbellulate bristles (sometimes also with shorter outer scales).
(c) Ward, Scott G - CC-BY
© Scott Ward
                                    18 Phyllaries in one series.
                                       19 Plants not herbaceous vines; flowers primarily yellow (sometimes yellow-orange); calyculus absent (or 1-2 indistinct bractlets); [natives or non-natives, collectively widespread]
                                         20 Pappus bristles white; flowers primarily yellow; [native and non-native, widespread]
                                           21 Disc florets sterile; stems bracteate but lacking leaves, the leaves simple; [non-native of disturbed habitats, ne US]
                                           21 Disc florets fertile; stems with leaves, the leaves simple to pinnately lobed (or otherwise compound); [natives and non-natives, widespread and of both intact and disturbed habitats].
                                             22 Stem leaves deeply toothed, pinnately lobed, or otherwise compound, not clasping or weakly so; plants perennial or rarely annuals (P. glabella)
                                             22 Stem leaves shallowly toothed to subentire, conspicuously clasping the stem; plants annuals
(c) Ward, Scott G
                                                 24 Pappus double, of both an inner (more apparent) series of longer bristles and an outer series consisting of short triangular scales or significantly shorter (and often coarser) bristles, these sitting more or less at the base of the inner pappus bristles (in Prionopsisthe outer bristles subtend the inner awns or scales).
                                                            29 Plants annuals with taproots; phyllaries linear to linear-lanceolate; inner pappus yellow to rust-colored proximally, outer pappus scale-like; disc florets bisexual and fertile (B. pilosa) or functionally staminate (B. hirtella)
                                                 24 Pappus simple, of only bristles and not with an additional series of reduced bristles or scales (sometimes pappus in 2-4 unequal series, or outer bristles progressively shortened in Xanthisma).
                                                                 31 Phyllaries spine-tipped with accompanying white margins (if lacking spine tips as in X. texanum, then inner phyllaries abruptly enlarged into ovate or sometimes elliptic blades 2-5 mm wide)
                                                                   32 Ray florets shorter, < 1.5 cm long (to 1.6 cm in Grindelia lanceolata); anthers not tailed (instead obtuse to sagittate), or if sagittate-tailed, then plants foul-smelling (as in Dittrichia, a waif in ne. US).
                                                                     33 Plants scentless, or if bearing an odor, not foul-smelling; anthers cuneate to sagittate at the base, but not tailed; [widespread natives, rarely e. US waifs otherwise native to w. US].
                                                                           36 Phyllaries in 1-2 equal/subequal series (outer minute bracts sometimes present); stem leaves shallowly toothed to subentire, conspicuously clasping the stem; plants annuals; [tribe Senecioneae)
                                                                                  39 Leaves toothed, proximal leaves petiolate; faces of cypselae variously textured (smooth, striate, furrowed, or rugose); pappus readily falling, of 2-3 smooth to setiform awns OR subulate scales 2.5-8 mm long (sometimes with up to 6-8 total barbellulate/setiform awns in G. squarrosa, G. lanceolata, and G. texana)