1	Plants usually with prickles (at least on basal parts or on young plants) and usually with stellate hairs (except in S. capsicoides); anthers narrow and tapered, dehiscent by terminal pores.		(2)
+	Plants without prickles, with or without stellate hairs; anthers of various forms, dehiscent by terminal pores that often open into longitudinal slits or by introrse longitudinal slits.		(26)
2 (1)	Leaves 1–3 times deeply pinnatifid (divided more than halfway to midrib) to compound; fruits nearly to completely covered by accrescent prickly calyx.		(3)
+	Leaves entire or lobed, rarely deeply pinnatifid or compound; fruiting calyces not accrescent or, if accrescent, not almost completely covering fruits.		(11)
3 (2)	Corollas radially symmetric; stamens equal or nearly so; calyces loosely covering red, juicy fruits		43 Solanum sisymbriifolium
+	Corollas bilaterally symmetric; stamens dimorphic, with one much longer than others; calyces tightly covering brown, dry fruits.		(4)
4 (3)	Stem hairs stellate or otherwise branched; corollas yellow		39 Solanum rostratum
+	Stem hairs mostly simple, often glandular (sometimes mixed with sparse stel­late hairs); corollas violet, blue, white, or yellow.		(5)
5 (4)	Corollas white or yellow.		(6)
+	Corollas violet or blue.		(7)
6 (5)	Stems with well-spaced, needlelike prickles; corollas white, 2–2.5 cm diam., rotate-stellate, with abundant interpetalar tissue; w Texas		9 Solanum cordicitum
+	Stems with dense, bristlelike prickles; corollas yellow, 1.3–1.8 cm diam., stellate, with sparse interpetalar tissue; s Arizona		27 Solanum lumholtzianum
7 (5)	Corollas 1–1.5 cm diam.; long anther 2–5 mm.		(8)
+	Corollas 1.4–3.5 cm diam.; long anther 5.5–20 mm.		(9)
8 (7)	Stems densely pubescent with simple, glandular hairs 0.2–0.4 mm; stems sparsely to moderately prickly, with 20 or fewer prickles per cm; corollas pentagonal-stellate, with sparse interpetalar tissue; endemic to nc New Mexico		34 Solanum novomexicanum
+	Stems sparsely pubescent with simple, glandular hairs ca. 0.2 mm; stems densely prickly, with 30+ prickles per cm; corollas pentagonal, with abundant interpetalar tissue; w Texas to c New Mexico, Arizona		42 Solanum setigeroides
9 (7)	Plants perennials; seeds plump, 2.8–3.6 mm		46 Solanum tenuipes
+	Plants annuals; seeds flattened, 2.3–3 mm.		(10)
10 (9)	Long anther 11–16 mm; corollas 2.5–3.5 cm diam.; large leaves usually only 2 times pinnatifid, with obtuse to rounded ultimate lobes		8 Solanum citrullifolium
+	Long anther 5.5–8.5 mm; corollas 1.4–2 cm diam.; large leaves often 3 times pinnatifid, with acute ultimate lobes		10 Solanum davisense
11 (2)	Leaves sessile or with petiole to 1 cm, blade rhombic; calyx lobes linear; corollas to 1–2 cm diam.; c Florida		23 Solanum jamaicense
+	Leaves with petiole (0.1–)1–10(–13) cm, blade lanceolate to oblong, elliptic, ovate, obovate, or suborbiculate; calyx lobes linear-lanceolate, lanceolate, triangular, deltate, ovate-lanceolate, elliptic-acuminate, or broadly deltate; corollas (1–)1.5–5 cm diam.		(12)
12 (11)	Pubescence of stems and upper leaf surfaces of unbranched hairs or plants glabrate.		(13)
+	Pubescence of stem and upper leaf surfaces of stellate hairs.		(14)
13 (12)	Pubescence eglandular or plants glabrate; berries orange to red; seeds winged		5 Solanum capsicoides
+	Pubescence glandular and eglandular; berries yellow, often mottled with green when young; seeds not winged		51 Solanum viarum
14 (12)	Pubescence dense and silvery or bright white, particularly on lower leaf surfaces.		(15)
+	Pubescence sparse to dense, of various colors, but not noticeably silvery or bright white.		(18)
15 (14)	Stellate hairs scalelike, with rays fused at center		17 Solanum elaeagnifolium
+	Stellate hairs not scalelike, rays all separate.		(16)
16 (15)	Leaves (0.5–)1–3(–4.5) cm wide		21 Solanum hindsianum
+	Leaves 3–15 cm wide.		(17)
17 (16)	Calyces not prickly; inflorescences usually much-branched; corollas usually blue to purple, rarely whitish; berries 0.7–1.5 cm diam., yellow to orange		26 Solanum lanceolatum
+	Calyces prickly; inflorescences unbranched or forked; corollas white to pale purple; berries 3.5–4(–5) cm diam., yellow		29 Solanum marginatum
18 (14)	Scandent shrubs with branches 1–2+ m; stems glabrate to sparsely pubes­cent; wet areas in Florida and Texas		45 Solanum tampicense
+	Erect or spreading herbs, shrubs, or small trees; stems noticeably stellate-pubescent; widespread, including Florida and Texas.		(19)
19 (18)	Leaf margins entire to very shallowly lobed; corollas stellate, without interpetalar tissue; berries red.		(20)
+	Leaf margins usually shallowly to deeply lobed, rarely entire, sub­entire, or sinuate; corollas rotate-campanulate, rotate-stellate, stellate-pentagonal, or stellate, with sparse to abundant interpetalar tissue; berries green, yellow, or purplish.		(21)
20 (19)	Inner surface of anther tube densely stellate-pubescent; inflores­cences usually unbranched; pedicels recurved to one side of axis in fruit		3 Solanum bahamense
+	Inner surface of anther tube glabrous; inflorescences branched; pedicels erect in fruit		14 Solanum donianum
21 (19)	Trees or shrubs 1–4 m; inflorescence pubescence of unbranched glandular hairs		47 Solanum torvum
+	Erect or spreading annual or perennial herbs or shrubs 0.2–1.2 m; inflorescence pubescence stellate.		(22)
22 (21)	Stems, inflorescences, and calyces densely armed; annual herbs, usually spreading and to 0.5(–1) m; major leaf lobes with acute teeth or shallow lobes		4 Solanum campechiense
+	Stems, inflorescences, and calyces sparsely to moderately armed; erect perennial herbs or shrubs 0.2–1.2 m; major leaf lobes, if present, entire to coarsely lobed.		(23)
23 (22)	Stems and petioles stellate-pubescent with central ray 1-celled and equal to or shorter than lateral rays		12 Solanum dimidiatum
+	Stems and petioles stellate-pubescent with central ray 1–5-celled and longer than lateral rays.		(24)
24 (23)	Plants to 0.2 m; leaf margins entire, sinuate, or shal­lowly lobed; inflorescences 1–4-flowered; endemic to dolomite outcrops in Alabama and possibly Georgia		38 Solanum pumilum
+	Plants to 1.2 m; leaf margins subentire, sinuate, or shallowly to deeply lobed; inflorescences 2–15-flowered; plants not confined to dolomite outcrops and distributions more widespread.		(25)
25 (24)	Stems armed with prickles to 6 mm; inflorescences unbranched or rarely forked; corollas 2–3 cm diam.; widespread in North America		6 Solanum carolinense
+	Stems armed with prickles to 15 mm; inflo­rescences forked to several times branched; corollas 2–4.4 cm diam.; mainly Alabama, Florida, and Georgia, rarely Mississippi		35 Solanum perplexum
26 (1)	Leaves compound; pedicels articulated above base.		(27)
+	Leaves simple, entire, undulate, sinuate-dentate to toothed, deeply lobed, pinnatifid, or hastate, simple to pinnately compound in S. seaforthianum; pedicels articulated at base.		(29)
27 (26)	Leaflets lobed; corollas yellow; plants without tubers; berries usually red, orange, or yellow		28 Solanum lycopersicum
+	Leaflets entire; corollas white to pink, blue, or purple; plants with underground tubers; berries green.		(28)
28 (27)	Corollas white, stellate; pseudostipules (when present) pinnatifid		24 Solanum jamesii
+	Corollas purple, blue, pale pink, or rarely white, pentagonal to rotate; pseudo­stipules entire		44 Solanum stoloniferum
29 (26)	Plants climbing or scrambling vines.		(30)
+	Plants herbs, subshrubs, shrubs, or small trees, not climbing.		(32)
30 (29)	Stamens (filaments) unequal; corollas purple; most leaves lobed or compound with up to 4 pairs of leaflets		41 Solanum seaforthianum
+	Stamens equal; corollas white or purple; leaves unlobed or with 1–3 basal lobes.		(31)
31 (30)	Corollas purple (rarely white) with green and white shiny spots at base of each lobe; n 2/3 of United States, s Canada		16 Solanum dulcamara
+	Corollas white or tinged with purple, often with shiny green or greenish white eye; Texas		49 Solanum triquetrum
32 (29)	Shrubs or small trees, 2–12 m; ovaries and berries pubescent.		(33)
+	Herbs, subshrubs, shrubs, or small trees, 0.1–2(–4) m; ovaries and berries glabrous.		(34)
33 (32)	Corollas white; without small axillary leaves		19 Solanum erianthum
+	Corollas purple; larger leaves often with smaller axillary leaves		30 Solanum mauritianum
34 (32)	Corollas 3–5 cm diam., usually pink to blue, violet, or purple, rarely whitish; shrubs or small trees, 1–4 m.		(35)
+	Corollas 2.5 cm or less diam., usually white to pale purple (pale to deep purple in S. umbelliferum); small herbs, subshrubs, or shrubs, to 1.5 m, rarely to 3 m.		(37)
35 (34)	Plants densely pubescent with usually glandular hairs; Santa Catalina Island, California		52 Solanum wallacei
+	Plants glabrous; California, Oregon.		(36)
36 (35)	Corolla lobes acute at apex; berries orange to red, sclerotic granules inconspicuous to absent		2 Solanum aviculare
+	Corolla lobes notched at apex; berries yellow to orange, sclerotic granules abundant		25 Solanum laciniatum
37 (34)	Corollas pale to deep purple or occasionally white, with green spots edged with white at base of lobes; anthers 3.5–4.5 mm		50 Solanum umbelliferum
+	Corollas white or tinged with purple, often with central star of different color but not with pronounced green spots at base of lobes; anthers 0.7–3.5(–5) mm.		(38)
38 (37)	Leaf margins deeply and regularly pinnatifid		48 Solanum triflorum (in part)
+	Leaf margins entire, or sinuate, sinuate-dentate, to shallowly toothed or lobed.		(39)
39 (38)	Plants noticeably glandular-pubescent, sticky to the touch.		(40)
+	Plants glabrous or eglandular-pubescent (sometimes with a few glandular hairs), not sticky to the touch.		(42)
40 (39)	Fruiting calyces not or only slightly accrescent, covering only base of fruit; plants glabrate to moderately pubescent; hairs mostly eglandular but occasionally glandular, to 1 mm		32 Solanum nigrum (in part)
+	Fruiting calyces strongly accrescent, covering at least half of fruit; plants moderately to densely pubescent; hairs glandular, 1.5–2 mm.		(41)
41 (40)	Fruiting calyces covering ca. half of fruit; berries shiny greenish to purplish brown, with (0–)2–3 sclerotic granules; inflorescences usually extra-axillary, 4–8(–10)-flowered		33 Solanum nitidibaccatum
+	Fruiting calyces nearly covering fruit; berries dull pale green, with 4–6 sclerotic granules; inflorescences usually leaf-opposed, 2–5(–7)-flowered		40 Solanum sarrachoides
42 (39)	Berries yellow, orange, or red when ripe; fruiting pedicels erect; inflores­cences leaf-opposed.		(43)
+	Berries green, white, yellowish green, or purple to purplish black when ripe; fruiting pedicels erect, spreading, recurved, reflexed, or nodding; inflorescences leaf-opposed or extra-axillary.		(44)
43 (42)	Shrubs 1–2 m, glabrous or minutely puberulent; corollas 0.7–1 cm diam.; anthers 1.5–2 mm; berries orange when ripe		13 Solanum diphyllum
+	Shrubs to 1 m, glabrous or densely pubescent with branched hairs; corollas 1–1.5(–2.5) cm diam.; anthers 3–4 mm; berries yellow, orange, or red when ripe		36 Solanum pseudocapsicum
44 (42)	Inflorescences nearly sessile; berries white to greenish and semi­transparent		11 Solanum deflexum
+	Inflorescences 0.5–4 cm; berries green, dark green, yellowish green, or purple to purplish black.		(45)
45 (44)	Anthers 0.7–1.5 mm.		(46)
+	Anthers (1.8–)2–4.5 mm.		(47)
46 (45)	Berries shiny purplish black, with (0–)2–4(–6) sclerotic gran­ules; fruiting pedicels erect or spreading; calyx lobes strongly reflexed in fruit		1 Solanum americanum
+	Berries dull or slightly shiny purple-black, with 6–9 sclerotic granules; fruiting pedicels reflexed or recurved; calyx lobes appressed to spreading in fruit		18 Solanum emulans
47 (45)	Fruiting peduncles sharply reflexed from base		7 Solanum chenopodioides
+	Fruiting peduncles spreading or curved downwards.		(48)
48 (47)	Berries without sclerotic granules (S. pseudogracile rarely with 2).		(49)
+	Berries with sclerotic granules.		(50)
49 (48)	Fruiting pedicels usually spreading, occasionally recurved; inflorescences racemelike; seeds 1.8–2 × 1.5–1.6 mm		32 Solanum nigrum (in part)
+	Fruiting pedicels recurved to reflexed; inflorescences umbel-like; seeds 1–1.3 × 0.8–0.9 mm		37 Solanum pseudogracile
50 (48)	Inflorescences forked, 6–14-flowered; w coast from California to Washington		20 Solanum furcatum
+	Inflorescences unbranched, 1–14-flowered; w coast to c and se United States, w, c Canada.		(51)
51 (50)	Plants decumbent to prostrate, fleshy; sclerotic granules 13–30 per fruit		48 Solanum triflorum (in part)
+	Plants erect to sprawling, not fleshy; sclerotic granules 2–13 per fruit.		(52)
52 (51)	Anthers (2.5–)3–4.5 mm, slightly tapered towards the tips; corollas 1–2 cm diam.		15 Solanum douglasii
+	Anthers 1.8–3 mm, not tapered; corollas 0.5–1.5 cm diam.		(53)
53 (52)	Sclerotic granules 2–4 per fruit; seeds 1.8–2 × 1.5–1.6 mm		22 Solanum interius
+	Sclerotic granules (4–)5–6(–13) per fruit; seeds 1.2–1.5 × 1–1.1 mm		31 Solanum nigrescens