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Keyed in multiple places:

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Key to Asteraceae, Key M: Herbaceous composites with the leaves alternate or basal and the heads radiate, the rays white, pink, purple, and with a pappus of bristles only

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1 Head 1 per plant (individual rosette); stems 0.1-0.3 dm tall; [TX and OK westwards]
1 Heads 5-300+ per (well-developed) plant; stems 0.3-35 dm tall; [collectively widespread].
..2 Stems with numerous thorns (1-2 cm long, modified axillary branches), and few or no leaves
..2 Stems leafy, not armed with thorns.
....3 Leaves unlobed; plant perennial from caudices, crowns, or rhizomes.
......4 Annuals from taproots; ray florets 0.3-7 mm long.
........5 Ray laminae 0.3-1.0 mm long; cypselas 1.0-1.5 mm long, compressed, 1-nerved on each face
........5 Ray laminae 1.3-7 mm long; cypselas (1.2-) 1.5-2.7 (-3) mm long, compressed or not, 5-18-nerved.
..........6 Disc flowers 25-35 per head; ray flowers in 1 series
......4 Perennials from caudices, crowns, or rhizomes; ray florets > 3 mm long.
............ 7 Basal and lower stem leaves petiolate, with blades cordate to rounded at the base
............ ..8 Heads borne in corymbiform arrays, the branches often subtended by large and leaf-like bracts; phyllaries < 2.5 (-3)× as long as wide, often > 1 mm wide; plants (in most species) colonial by rhizomes; rays (in most species) white; phyllaries (in many species) glandular
............ ..8 Heads borne in paniculiform arrays, the branches bearing small and narrow bracts; phyllaries > 3× as long as wide, often < 1 mm wide; plants (in most species) solitary; rays (in most species) blue, violet, or pink; phyllaries eglandular
............ 7 Basal and lower stem leaves sessile (sometimes cordate-clasping), or if petiolate then with cuneate to attenuate bases.
............ ....9 Rays pink, purple, lavender, blue, or pale pink [plants with pale pink rays may need to be keyed both ways].
............ ......10 Heads borne in paniculiform or in diffuse and irregular arrays
............ ......10 Heads borne either in flat-topped or rounded, corymbose arrays, or in narrow racemiform or spiciform panicles, or solitary.
............ ........11 Leaves 1.2-4.0 cm long, 1-4 mm wide, stiff, scabrous margined and weakly spine-tipped; plants 1-7 dm tall; pappus in 2 series, the inner much longer than the outer (ca. 1 mm long) bristles
............ ........11 Leaves either longer or broader or both, herbaceous; Leaves (5-) 13-45 mm wide, herbaceous, neither scabrous-margined nor spine-tipped; plants 4-30 dm tall; pappus not divided into distinct inner and outer series.
............ ..........12 Plants 10-35 dm tall; larger leaves (basal or low on the stem) with cuneate or attenuate bases, the blades 30-50 cm long; [non-native, rarely persistent or spreading from horticultural use]
............ ..........12 Plants 1-12 dm tall; larger leaves with blades 2-20 cm long; [natives, collectively widespread and common in our region]
............ ....9 Rays white (or very slightly pink-flushed).
............ ............ 13 Heads borne in paniculiform or in diffuse and irregular arrays
............ ............ 13 Heads borne either in flat-topped or rounded, corymbose arrays, or in narrow racemiform/spiciform panicles, or solitary.
............ ............ ..14 Heads arrayed in 1 (or more) cylindrical thyrses
............ ............ ..14 Heads borne in either narrow racemiform/spiciform panicles, or in corymbose arrays.
............ ............ ......16 Disc flowers yellow (and often fading to pink or purplish).
............ ............ ........17 Rays 2-7, the ray ligules 2-11 mm long, often twisted or contorted; phyllaries whitish with a distinct green tip, the green area about as wide as long
............ ............ ........17 Rays (8-) 9-40, the ray ligules 4-20 mm long, generally planar (or neatly coiling at post-maturity); phyllaries various.
............ ............ ..........18 Pappus double, with an outer set of bristles < 1 mm long; leaves entire
............ ............ ..........18 Pappus not divided into distinctively different outer and inner series; leaves toothed or entire.

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

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1 Receptacles chaffy (paleate).
..2 Phyllaries dry, scarious-margined.
....3 Ray florets 1-5 mm long; heads small in corymbiform arrays
....3 Ray florets > 5 mm long; heads large, terminating the branches
..2 Phyllaries herbaceous, not scarious on margins.
......4 Ray florets < 2.5 mm long; disk florets sterile, with an undivided style
......4 Ray florets > 5 mm long; disk florets fertile, with a divided style.
........5 Ray florets pink or light purple, > 15 mm long; heads single
........5 Ray florets white, 5-10 mm long; heads 20-100 in a compound corymb
1 Receptacles naked (epaleate).
............ 7 Achene faces minutely glandular-glochidiate (bearing small gland-like bristles)
............ ..8 Leaves basal; cypselae marginally 2-ribbed; mature plants < 2 dm tall
............ ..8 Leaves cauline (and sometimes also basal); cypselae with ± 10 ribs; mature plants > 2 dm tall
............ ....9 Heads solitary or 2-3 in corymbiform arrays
............ ....9 Heads 5-60+ in corymbiform arrays
..........6 Pappus present, of bristles or scales.
............ ......10 Heads primarily discoid with reduced ray florets
............ ......10 Heads radiate with conspicuous ray florets.
............ ........11 Taprooted annuals; ray florets 1-7 mm long.
............ ..........12 Leaves and stems not fleshy, rarely glabrous; cypselas < 1.4 mm long
............ ..........12 Leaves and stems fleshy, mostly glabrous; cypselas > 1.4 mm long
............ ........11 Not taprooted and mostly perennials; ray florets > 3 mm long.
............ ............ 13 Ray florets usually > 60; blooming Apr-Oct
............ ............ 13 Ray florets usually < 60; blooming late May-Nov.
............ ............ ..14 Receptacles hemispheric to conic; pappus often with 2-4 awns (Boltonia) or lacking awns and coroniform (Astranthium).
............ ............ ....15 Achenes not narrowly winged, the surfaces minutely glandular-glochidiate (bearing small gland-like bristles)
............ ............ ....15 Achenes narrowly winged, the surfaces sometimes puberulent but not glandular-glochidiate
............ ............ ..14 Receptacles flat to slightly convex; pappus lacking awns.
............ ............ ......16 At least the basal and lower leaves both petiolate and cordate/subcordate at base.
............ ............ ........17 Often colonial; inflorescence corymbiform, flat-topped or rounded; outer phyllaries > 1 mm broad
............ ............ ......16 Basal and lower leaves not both petiolate and cordate/subcordate at base.
............ ............ ............ 19 Cypselas not glandular; pappus single or double or in four series.
............ ............ ............ ..20 Leaves silvery-silky on both sides (at least when young), entire
............ ............ ............ ....21 Pappus double, with inner bristles distinctly longer than outer bristles.
............ ............ ............ ....21 Pappus simple with all bristles often about the same length.
............ ............ ............ ........23 Ray florets white, few (usually 3-8); cypselas densely silky
............ ............ ............ ........23 Ray florets white to pink or blue or purple, more numerous (usually 8-30); cypselas glabrous to pubescent but not densely silky.
............ ............ ............ ..........24 Ray florets white; involucres < 6 mm long; phyllaries < 1 mm wide
............ ............ ............ ..........24 Ray florets white or pink to blue or purple; involucres 7-12 mm long; phyllaries usually > 1 mm wide.
............ ............ ............ ............ ....27 Plants coarse-hairy; lowest leaves > 5 cm wide
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