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| 1 Ray florets yellow to orange. |
| ..2 Receptacles chaffy (paleate). |
| ....3 Disk florets sterile with style undivided |
| ....3 Disk florets fertile with style bifurcate. |
| ......4 Leaves decurrent down the stem; cypselas strongly flattened and often winged |
| ......4 Leaves not decurrent; cypselas moderately compressed, not winged. |
| ........5 Receptacular bracts connate to form a honeycomb-like structure in which the flowers are set; pappus of 7-12 scales |
| ........5 Receptacular bracts not fused; pappus of awns or a fused crown (coroniform). |
| ..........6 Receptacles flat |
| ..........6 Receptacles subspheric, conical or columnar. |
| ............ 7 Phyllary series unequal (outer longer than inner); cypselae strongly compressed; ray florets subtended by receptacular bracts |
| ............ 7 Phyllary series subequal; cypselae not strongly compressed; ray florets not subtended by receptacular bracts (only the disk flowers with bracts) |
| ..2 Receptacles naked (eplaeate), rarely with bristles. |
| ............ ..8 Pappus of scales or crowns (coroniform). |
| ............ ....9 Heads small, with disk < 5 mm wide and ray florets < 5 mm long |
| ............ ....9 Heads larger, with disk > 5 mm wide and ray florets > 5 mm long |
| ............ ......10 Stems usually winged; cypselae 4-5 angled |
| ............ ......10 Stems not winged; cypselae 3-4+ angled. |
| ............ ........11 Phyllaries in (3-) 4-9+ series; heads borne singly or in arrays; ray florets (the laminae) yellow or orange throughout |
| ............ ........11 Phyllaries in 2-3+ series; heads borne singly; ray florets (the laminae) often bicolored |
| ............ ..8 Pappus of bristles or setiform awns, sometimes also with shorter outer scales. |
| ............ ..........12 Phyllaries in one series. |
| ............ ............ 13 Disk florets fertile, stems with leaves |
| ............ ............ 13 Disk florets sterile, stems bracteate but lacking leaves |
| ............ ..........12 Phyllary in 2+ series. |
| ............ ............ ..14 Pappus double (the outer series consisting of shorter triangular-shaped scales; the inner series consisting of longer bristles). |
| ............ ............ ....15 Ray florets without pappus |
| ............ ............ ....15 Ray florets with pappus (similar to that of disk florets). |
| ............ ............ ......16 Leaves pinnately veined, usually broader and not grasslike |
| ............ ............ ......16 Leaves parallel-veined, linear and grasslike |
| ............ ............ ..14 Pappus simple, only in 1 series. |
| ............ ............ ........17 Ray florets > 1.5 cm long; anthers tailed |
| ............ ............ ........17 Ray florets < 1.5 cm long (to 1.6 cm in Grindelia lanceolata); anthers not tailed (instead obtuse to sagittate). |
| ............ ............ ..........18 Plants taprooted. |
| ............ ............ ............ 19 Leaves sessile throughout; cypsela faces strigose to sericeous |
| ............ ............ ............ 19 Proximal leaves petiolate, distal (upper) leaves sessile; cypsela faces smooth, striate, furrowed, or ± rugose |
| ............ ............ ..........18 Plants not taprooted, instead rhizomatous or with woody caudices. |
| ............ ............ ............ ..20 Inflorescences flat-topped corymbs; leaves resinous-punctate, narrow, entire, sessile or subsessile |
| ............ ............ ............ ..20 Inflorescences rarely flat-topped; leaves not resinous-punctate, usually not linear, often toothed and petiolate |
| 1 Ray florets white or whitish to pink or purple. |
| ............ ............ ............ ....21 Receptacles chaffy (paleate). |
| ............ ............ ............ ......22 Phyllaries dry, scarious-margined. |
| ............ ............ ............ ........23 Ray florets 1–5 mm long; heads small in corymbiform arrays |
| ............ ............ ............ ........23 Ray florets > 5 mm long; heads large, terminating the branches |
| ............ ............ ............ ......22 Phyllaries herbaceous, not scarious on margins. |
| ............ ............ ............ ..........24 Ray florets < 2.5 mm long; disk florets sterile, with an undivided style |
| ............ ............ ............ ..........24 Ray florets > 5 mm long; disk florets fertile, with a divided style. |
| ............ ............ ............ ............ 25 Ray florets pink or light purple, > 15 mm long; heads single |
| ............ ............ ............ ............ 25 Ray florets white, 5–10 mm long; heads 20-100 in a compound corymb |
| ............ ............ ............ ....21 Receptacles naked (epaleate). |
| ............ ............ ............ ............ ..26 Pappus absent. |
| ............ ............ ............ ............ ....27 Achene faces minutely glandular-glochidiate (bearing small gland-like bristles) |
| ............ ............ ............ ............ ....27 Achene faces glabrous or short-strigose but not glandular-glochidiate. |
| ............ ............ ............ ............ ......28 Heads with or without ray florets, if present these reduced in size and less conspicuous than the central, whitish disk florets |
| ............ ............ ............ ............ ......28 Heads with conspicuous ray florets; disk florets typically yellow-colored |
| ............ ............ ............ ............ ........29 Leaves basal; cypselae marginally 2-ribbed; mature plants < 2 dm tall |
| ............ ............ ............ ............ ........29 Leaves cauline; cypselae with ± 10 ribs; mature plants > 2 dm tall |
| ............ ............ ............ ............ ..26 Pappus present, of bristles or scales. |
| ............ ............ ............ ............ ..........30 Heads primarily discoid with reduced ray florets |
| ............ ............ ............ ............ ..........30 Heads radiate with conspicuous ray florets. |
| ............ ............ ............ ............ ............ 31 Taprooted annuals; ray florets 1–7 mm long. |
| ............ ............ ............ ............ ............ ..32 Leaves and stems not fleshy, rarely glabrous; cypselas < 1.4 mm long |
| ............ ............ ............ ............ ............ ..32 Leaves and stems fleshy, mostly glabrous; cypselas > 1.4 mm long |
| ............ ............ ............ ............ ............ 31 Not taprooted and mostly perennials; ray florets > 3 mm long. |
| ............ ............ ............ ............ ............ ....33 Ray florets usually > 60; blooming Apr-Oct |
| ............ ............ ............ ............ ............ ....33 Ray florets rarely < 60; blooming late May-Nov. |
| ............ ............ ............ ............ ............ ......34 Receptacles hemispheric to conic; pappus often with 2-4 awns (Boltonia) or lacking awns and coroniform (Astranthium). |
| ............ ............ ............ ............ ............ ........35 Achenes not narrowly winged, the surfaces minutely glandular-glochidiate (bearing small gland-like bristles) |
| ............ ............ ............ ............ ............ ........35 Achenes narrowly winged, the surfaces sometimes puberulent but not glandular-glochidiate |
| ............ ............ ............ ............ ............ ......34 Receptacles flat to slightly convex; pappus lacking awns. |
| ............ ............ ............ ............ ............ ..........36 At least the basal and lower leaves both petiolate and cordate/subcordate at base. |
............ ............ ............ ............ ............ ............ 37 Often colonial; inflorescence corymbiform, flat-topped or rounded; outer phyllaries > 1 mm broad |
| ............ ............ ............ ............ ............ ............ 37 Not colonial; inflorescence paniculiform, often elongate; outer phyllaries < 1 mm broad |
| ............ ............ ............ ............ ............ ..........36 Basal and lower leaves not both petiolate and cordate/subcordate at base. |
| ............ ............ ............ ............ ............ ............ ..38 Leaves sessile and auriculate or cordate-clasping |
| ............ ............ ............ ............ ............ ............ ..38 Leaves petiolate or epetiolate but not auriculate or cordate-clasping. |
| ............ ............ ............ ............ ............ ............ ....39 Cypselas glandular; pappus double |
| ............ ............ ............ ............ ............ ............ ....39 Cypselas not glandular; pappus single or double or in four series. |
| ............ ............ ............ ............ ............ ............ ......40 Leaves silvery-silky on both sides (at least when young), entire |
| ............ ............ ............ ............ ............ ............ ......40 Leaves not silvery-silky, entire or toothed. |
| ............ ............ ............ ............ ............ ............ ........41 Pappus double, with inner bristles distinctly longer than outer bristles. |
| ............ ............ ............ ............ ............ ............ ..........42 Leaves not rigid, veiny, lanceolate to elliptic or ovate, > 6 mm wide |
| ............ ............ ............ ............ ............ ............ ..........42 Leaves rigid, 1-nerved, linear to linear-spatulate, < 5 mm wide |
| ............ ............ ............ ............ ............ ............ ........41 Pappus simple with all bristles often about the same length. |
| ............ ............ ............ ............ ............ ............ ............ 43 Ray florets white, few (usually 3–8); cypselas densely silky |
| ............ ............ ............ ............ ............ ............ ............ 43 Ray florets white to pink or blue or purple, more numerous (usually 8–30); cypselas glabrous to pubescent but not densely silky. |
| ............ ............ ............ ............ ............ ............ ............ ..44 Ray florets white; involucres < 6 mm long; phyllaries < 1 mm wide |
| ............ ............ ............ ............ ............ ............ ............ ..44 Ray florets white or pink to blue or purple; involucres 7–12 mm long; phyllaries usually > 1 mm wide. |
| ............ ............ ............ ............ ............ ............ ............ ....45 Phyllaries glandular |
| ............ ............ ............ ............ ............ ............ ............ ....45 Phyllaries not glandular. |
| ............ ............ ............ ............ ............ ............ ............ ......46 Phyllaries long-attenuate or loose and spreading |
| ............ ............ ............ ............ ............ ............ ............ ......46 Phyllaries appressed, not long-attenuate. |
| ............ ............ ............ ............ ............ ............ ............ ........47 Plants coarse-hairy; lowest leaves > 5 cm wide |
| ............ ............ ............ ............ ............ ............ ............ ........47 Plants glabrous to hairy; lowest leaves < 3 cm wide |