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Key to Vernonia

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1 Leaves basally disposed (the larger leaves in a basal rosette or in the lower half of the stem, the leaves strongly reduced in size upwards); [mainly Coastal Plain and adjacent areas of inland provinces]

2 Larger leaves basal, borne flat against the ground; larger leaves (21-) 60-75+ mm wide  Vernonia acaulis

2 Larger leaves basally disposed, mainly on the lower stem; larger leaves 2-25 mm wide.

3 Larger leaves 5-25 mm wide; leaf L:W ratio 3-17.

4 Phyllary tips subulate.  Vernonia ×georgiana

4 Phyllary tips acute to rounded (sometimes minutely apiculate), the narrowest short acuminate.

5 Leaves 2-8+ mm wide; lower leaf surface scabrellous with awl-shaped, appressed hairs; plants 2-3 (-5) dm tall; [FL peninsula]  Vernonia blodgettii

5 Leaves (5-) 12-25 mm wide; lower leaf surface glabrate, with awl-shaped hairs sunken in pits; plants 4-8 (-10+) dm tall; [AL westwards to OK and TX]  Vernonia texana

3 Larger leaves 2-4 (-8) mm wide; leaf L:W ratio (8-) 12-30 (-60+).

6 Flowers 8-15 per head; outer phyllaries 1.4-3.9 mm long, their tips acute to acuminate; involucres 4.0-6.0 mm high; [wc. and se. GA south to c. peninsular FL and west to s. MS]  Vernonia angustifolia var. mohrii

6 Flowers 16-30 per head; outer phyllaries 1.8-7.2 mm long, their tips acuminate to long acuminate; involucres 5.0-10.0 mm high; [wc. and se. GA northeast to s. NC].

7 Flowers 16-19 per head; outer phyllaries 1.8-4.8 mm long, their tips acuminate to long acuminate; involucres 5.0-7.0 mm high; [wc. and se. GA northeast to s. NC].  Vernonia angustifolia var. angustifolia

7 Flowers 20-30 per head; outer phyllaries 3.9-7.2 mm long, their tips long acuminate; involucres 6.5-10.0 mm high; [wc. and se. GA northeast to c. SC].  Vernonia angustifolia var. scaberrima

1 Basal rosette absent; [collectively of a wide variety of habitats].

Show caption*© Paul Marcum                8 Phyllary tips subulate to filiform, at broadest at least acuminate.

9 Involucres 11-15 mm in diameter; phyllaries (50-) 60-70+; florets 50-100+  Vernonia arkansana

9 Involucres 4-8 (-11) mm in diameter; phyllaries 22-46 (-60+); florets 10-45 (-65).

10 Leaf L:W ratio 8-20 (-30+); leaves (2.5-) 8-12+ mm wide; plants 3-5 (-8+) dm tall; [OK, TX, westwards]  Vernonia marginata

10 Leaf L:W ratio 2.5-6+; leaves (5-) 10-45 (-70+) mm wide; plants 4-30 dm tall; [collectively widespread east of the Mississippi River].

11 Middle cauline leaves 0.1-1.8 cm wide; plants 3-11 dm tall; [Coastal Plain of GA and SC, pinelands].  Vernonia pulchella

11 Middle cauline leaves 1.2-7.5 cm wide; plants 4-35 dm tall; [collectively widespread east of the Mississippi River, of various habitats, but not typically in Coastal Plain pinelands].

12 Pappus whitish to yellowish, 30 outer bristles intergrading with 30+ inner bristles; leaf blades 2.5-3.5 (-4)× as long as wide  Vernonia glauca

Show caption*© Scott Ward                        12 Pappus brown to purple, 20 outer scales contrasting with 30-40+ inner bristles; leaf blades (3.3-) 4-6× as long as wide  Vernonia noveboracensis

Show caption*© Scott Ward                8 Phyllary tips acute to rounded (sometimes minutely apiculate), the narrowest short acuminate.

13 Broadest leaves on a plant < 10 mm wide; leaves (even the broadest) 7-50× as long as wide.

14 Lower leaf surface glabrate and pitted (with awl-shaped hairs in the pits); flowers 9-15 per head; [mainly Ouachita Mountains, of AR and OK]  Vernonia lettermanii

14 Lower leaf surface densely silky tomentose; flowers 12-29 per head; [TX and extreme sw. AR]  Vernonia lindheimeri

13 Broadest leaves on a plant > 10 mm wide; leaves 2-10× as long as wide (at least the broadest <7× as long as wide).

15 Undersurface of leaf glabrous or nearly so, with pits (best seen at > 10× magnification) containing awl-shaped hairs or glands  Vernonia fasciculata var. fasciculata

15 Undersurface of leaves conspicuously scabrous or pubescent, lacking pits.

16 Stems glabrous  Vernonia flaccidifolia

16 Stems hairy.

17 Leaf undersurfaces scabrous with appressed awl-shaped hairs, with few or no resin glands.

18 Heads with 13-30 flowers; leaf blades linear-lanceolate, 10-30 cm long, 1.2-7.5 cm wide, 4-10× as long as wide; involucre 2.3-5.5 mm wide; phyllaries 1.2-3.1 mm wide  Vernonia gigantea

18 Heads with 9-20 flowers; leaf blades elliptic to oblanceolate, 6-20 cm long, 1.2-5 cm wide, 3-5× as long as wide; involucre 2.0-4.0 mm wide; phyllaries 0.9-1.8 mm wide  Vernonia ovalifolia

17 Leaf undersurfaces with curled, erect hairs, and with conspicuous resin glands.

19 Heads with 30-55 florets; involucres (6-) 7-10 mm high, 5-9 mm wide  Vernonia missurica

19 Heads with (15-) 20-25 (-35) florets; involucres 4-6.7 mm high, 4-7 mm wide.

20 Flowers mostly 23-34 per head; inner phyllaries with tips recurved, pubescent on the inner surface; [mainly Ozarkian]  Vernonia baldwinii var. baldwinii

20 Flowers mostly 17-27 per head; inner phyllaries loosely spreading, glabrous; [mainly Plainsian, also weedy and adventive]  Vernonia baldwinii var. interior