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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 pinnatifid to bipinnatifid; plant annual |
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 |
6 Disc flowers 4-10 (-13) per head; ray flowers in 1-3 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]. |
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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. |
15 Heads borne in narrow racemiform/ spiciform panicles |
15 Heads borne in corymbose arrays. |
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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. |
19 Achenes not glandular, either glabrous or strigillose |
19 Achenes densely gland- dotted |
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 |
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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). |
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7 Achene faces minutely glandular- glochidiate (bearing small gland-like bristles) |
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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 |
17 Not colonial; inflorescence paniculiform, often elongate; outer phyllaries < 1 mm broad |
16 Basal and lower leaves not both petiolate and cordate/subcordate at base. |
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19 Cypselas glandular; pappus double |
19 Cypselas not glandular; pappus single or double or in four series. |
20 Leaves silvery-silky on both sides (at least when young), entire |
20 Leaves not silvery-silky, entire or toothed. |
21 Pappus double, with inner bristles distinctly longer than outer bristles. |
22 Leaves not rigid, veiny, lanceolate to elliptic or ovate, > 6 mm wide |
22 Leaves rigid, 1-nerved, linear to linear- spatulate, < 5 mm wide |
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. |
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26 Phyllaries long- attenuate or loose and spreading |
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27 Plants coarse-hairy; lowest leaves > 5 cm wide |
27 Plants glabrous to hairy; lowest leaves < 3 cm wide |