Many species in this family are unpleasant-smelling and/or clammy-pubescent. Many are poisonous or thought to be so, although persons vary in their responses, and plants may vary with age or geography. Strong drugs are obtained from some species. Notable edible species include the white potato (Solanum tuberosum), eggplant (S. melongena), tomato (S. lycopersicum), and species of Capsicum (the hot peppers, sweet peppers, paprika, Tabasco and chili peppers, and their kin, all natives of the New World, but though some are waifs, none established outside of cultivation in our region).

1. Flowers all or mostly more than 1 at a node, in peduncled inflorescences or on axillary pedicels (at least on older woody stems in Lycium).

2. Plant woody; leaves all simple, unlobed, entire, glabrous, less than 1.8 (-4) cm wide; flowers on slender glabrous pedicels in axils of foliage leaves (opposite or tightly clustered, at least on older stems).

Lycium

2. Plant herbaceous (or somewhat woody toward base); leaves entire, sinuate to deeply lobed, or compound, at least slightly pubescent, the largest (2-) 3-22 cm wide; flowers in peduncled inflorescences or on hairy pedicels.

3. Lobes of corolla nearly as long as the tube or longer; leaves (except youngest) usually irregularly sinuate to deeply lobed or compound.

Solanum

3. Lobes of corolla much shorter than the tube; leaves entire.

4. Corolla ± flat (rotate), white (with yellow star-like center); flowers all or mostly clustered in axils of leaves; fruit a berry closely enclosed in the enlarged calyx.

Leucophysalis

4. Corolla with elongate tube, greenish yellow or entirely white; flowers in branched inflorescence; fruit a capsule.

Nicotiana

1. Flowers all one per node (solitary in the axils of leaves or bracts) or between nodes (developing a terminal, bracted spike in Hyoscyamus).

5. Plant with either auriculate-clasping leaves or with calyx ca. (3-) 3.5-9 (-11.5) cm long; fruit a capsule.

6. Cauline leaves petiolate, not clasping; corolla ca. 7.5-20 cm long with no reticulate pattern; calyx ca. (3-) 3.5-9 (-11.5) cm long but shed at maturity to expose the conspicuously spiny dehiscent fruit.

Datura

6. Cauline leaves auriculate-clasping at the base; corolla less than 3.5 cm long, reticulate-veiny (purple on yellow-green petals); calyx not over 2.5 cm long but completely enclosing the smooth circumscissile capsule.

Hyoscyamus

5. Plant with neither auriculate-clasping leaves nor calyx over 3.5 cm long (except in fruit in some species of Physalis); fruit a capsule (not often seen) or a berry.

7. Corolla yellow (whitish in one rarely escaped species); lobes of calyx shorter than the tube.

Physalis

7. Corolla blue to red or purple or sometimes white; lobes of calyx distinctly longer than the tube.

8. Flowers over 4 cm long, erect or ascending; fruit a capsule, not covered by the calyx; stems clammy-pubescent with multicellular hairs.

Petunia

8. Flowers less than 4 cm long, nodding; fruit a berry, covered by or at least with conspicuous enlarged calyx; stem glabrous to pubescent.

9. Leaves entire; calyx lobes ovate-lanceolate, scarcely overlapping at base; berry merely subtended by enlarged calyx lobes; plant perennial.

Atropa

9. Leaves coarsely toothed; calyx lobes broadly ovate, overlapping; berry enclosed in enlarged calyx; annual.

Nicandra