Key to Wisconsin Solanum

Author: Theodore S. Cochrane

• 1a.Plant spiny and otherwise rather copiously stellate-pubescent; corolla 20–30 mm wide 2

• 1b.Plant unarmed, the pubescence, when present, entirely of simple hairs; corolla 4–11 mm wide (except 20–40 mm in S. tuberosum). 3

• 2a.Calyx merely stellate or occasionally the tube with 1 or 2 short spines, loosely cupping the base of the ripe berry; corolla white to pale violet; leaves subentire to irregularly sinuate or shallowly few-lobed; perennial, the roots deep, often rhizome-like S. carolinense

• 2b. Calyx spiny, closely and fully enclosing the berry; corolla yellow; leaves once or twice pinnately lobed, cleft, or parted; annual, tap-rooted S. rostratum

• 3a.Corolla lemon yellow; anthers opening by longitudinal slits; leaves pinnately compound, the leaflets serrate to incised or basally pinnatisect S. lycopersicum

• 3b.Corolla white or purple; anthers opening by terminal pores; leaves mostly simple (some leaves with 1 to 4 (5) basal lobes or leaflets in S. dulcamara), the margins irregularly and bluntly toothed to sinuate or entire 4

• 4a. Stem straggling, clambering, or climbing, herbaceous or soft-wooded below; corolla violet or purple with a pair of yellow-green spots below each reflexed lobe (occasionally white); berries red at maturity S. dulcamara

• 4b.Stem erect, ascending, or spreading, strictly herbaceous; corolla white to faintly bluish; berries black or olive to brownish or purplish green at maturity 5

• 5a. Plant ± densely villous-hirsute with often gland-tipped hairs; calyx enlarging after anthesis, 4–6 (–9) mm long, cupping the lower half of the dark green to green-brown berry S. nitidibaccatum

• 5b. Plant glabrous or very sparsely strigose with eglandular hairs; calyx scarcely enlarging, at maturity 2–3 mm long, not cupping the black berry S. emulans

Many species (perhaps all) have some parts that contain the toxin solanine, and parts may be edible only at certain times and poisonous at others. All parts of horse-nettle, buffalo-bur, and bittersweet nightshade, including their tomato-like fruits, are poisonous to humans and livestock to varying degrees.

Solanum includes the potato, S. tuberosum L., collected once by P. Blatchford (s.n., F) at Lake Geneva in 1875, the three labels lacking any hint as to habitat or status. Plants have trailing shoots that form tubers and leaves with 7 to 9 large leaflets alternating with small ones.