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| 1 Receptacles with paleae or bristles. |
| ..2 Pappus lacking or of scales or awns. |
| ....3 Pappus lacking. |
| ......4 Involucre of dentate or fimbriate phyllaries |
| ......4 Involucre of the pistillate heads a bur with hooked prickles |
| ....3 Pappus present. |
| ........5 Phyllaries dentate or fimbriate |
| ........5 Phyllaries entire |
| ..2 Pappus of bristles. |
| ..........6 Phyllaries fimbriate, dentate, or spiny; leaves often prickly or spiny |
| ..........6 Phyllaries entire, leaves not prickly or spiny. |
| ............ 7 Basal leaves 1-5 mm wide; outer florets pistillate |
| ............ 7 Basal leaves > 5 mm wide (except in Liatris pseudoliatris); florets all perfect. |
| ............ ..8 Phyllaries hooked at tip; heads forming burs at maturity |
| ............ ..8 Phyllaries not hooked at tip; heads not forming burs at maturity. |
| ............ ....9 Heads larger, the involucre 6-15 mm high, with 15-40 phyllaries; leaves with conspicuous (at least at 10× magnification) resin dots |
| ............ ....9 Heads small, the involucre 3.5-6 mm high, with 5-12 phyllaries; leaves without shining punctate glands (except punctate-glandular in Litrisa, of the FL peninsula). |
| ............ ......10 Stem with punctate glands; peduncles punctate-glandular and also hirsutulous; pappus bristles in 2 series; [of FL peninsula] |
| ............ ......10 Stem eglandular, glabrous or spreading-hirsute; peduncles glabrous or stipitate-glandular; pappus bristles in 1 series; [widespread in the Coastal Plain] |
| 1 Receptacles naked. |
| ............ ........11 Pappus lacking or of scales or awns. |
| ............ ..........12 Disk florets blue or purple. |
| ............ ............ 13 Heads few-flowered, aggregated into secondary heads with leafy bracts |
| ............ ............ 13 Heads many-flowered, not aggregated into secondary heads |
| ............ ..........12 Disk florets yellow to yellowish green or reddish to reddish brown. |
| ............ ............ ..14 Cypselas winged and spined; heads sessile in the branch forks |
| ............ ............ ..14 Cypselas not winged and spined; heads not sessile in the branch forks. |
| ............ ............ ....15 Inflorescence elongate, paniculiform, spiciform, or racemiform |
| ............ ............ ....15 Inflorescence a flat-topped corymb, or heads solitary. |
| ............ ............ ......16 Receptacle strongly convex and pointed; plants pineapple-scented |
| ............ ............ ......16 Receptacle flat to convex; plants scented, but not of pineapple |
| ............ ........11 Pappus of barbellate or plumose bristles. |
| ............ ............ ........17 Heads yellow. |
| ............ ............ ..........18 Perennial; leaves remotely toothed to entire; [of shale barrens] |
| ............ ............ ..........18 Annual; leaves irregularly toothed to pinnatifid; [weed of disturbed soil] |
| ............ ............ ........17 Heads white, whitish, pink, purple, red, |
| ............ ............ ............ 19 Florets all perfect. |
| ............ ............ ............ ..20 Larger leaves hastate; heads whitish |
| ............ ............ ............ ..20 Leaves not hastate; heads whitish to red or pink to violet or deep purple. |
............ ............ ............ ....21 Phyllaries in essentially one series; leaves palmately veined, ovate to reniform |
| ............ ............ ............ ....21 Phyllaries in several series; leaves variously veined, linear to broadly ovate. |
| ............ ............ ............ ......22 Heads white or whitish; [of uplands] |
| ............ ............ ............ ......22 Heads pink to red or violet to deep purple or, rarely, white; [of uplands or wetlands]. |
| ............ ............ ............ ........23 Pappus bristles of one length |
| ............ ............ ............ ........23 Pappus double with inner bristles long and the outer very short |
| ............ ............ ............ 19 Some or all florets pistillate. |
| ............ ............ ............ ..........24 Leaves not white-woolly. |
| ............ ............ ............ ............ 25 Phyllaries in essentially one series; fresh plants not strongly scented |
| ............ ............ ............ ............ 25 Phyllaries in several series; fresh plants with a strong, aromatic fragrance |
| ............ ............ ............ ..........24 Leaves white woolly or gray-tomentose, at least beneath (abaxially). |
| ............ ............ ............ ............ ..26 Plants dioecious. |
| ............ ............ ............ ............ ....27 Blooming Jul-Sep; leaves numerous on stem |
| ............ ............ ............ ............ ....27 Blooming Mar-May; leaves basally disposed |
| ............ ............ ............ ............ ..26 Plants not dioecious. |
| ............ ............ ............ ............ ......28 Bristles plumose; pappi persistent |
| ............ ............ ............ ............ ......28 Bristles barbellate to barbellulate; pappi falling |
| ............ ............ ............ ............ ........29 Pappus bristles united at their base, falling as units. |
| ............ ............ ............ ............ ..........30 Blooming Mar-Jul; phyllaries in 3-7 series, sometimes tinged with purple or brown but lacking a conspicuous dark brown spot |
| ............ ............ ............ ............ ..........30 Blooming Jul-Oct; phyllaries in 2-3 series, some or all phyllaries bearing a conspicuous (distal-middle) dark brown spot |
| ............ ............ ............ ............ ........29 Pappus bristles distinct, not united at the base and falling seperately. |
| ............ ............ ............ ............ ............ 31 Involucre < 4 mm; mature plants > 25 cm tall |
| ............ ............ ............ ............ ............ 31 Involucre 4-8 mm; mature plants usually > 2 dm tall |