The twoleaf nightshade (Solanum diphyllum Linnaeus) is a woody shrub native to mesic open forests of Mexico and Central America. It is cultivated in China and Taiwan as an ornamental and for hedges and was introduced to gardeners in the southern US. Because it 'escapes', the plant is no longer available in the horticultural trade.

Twoleaf nightshade has shiny unequal paired leaves; one is large and elliptic, the other small and rounded. The drooping white flowers have five recurved petals and stamens with large yellow anthers. The flowers are pollinated by wasps, bees, and flies—the vibration of the wings causes the anthers to release the pollen. The many-seeded berries ripen to yellow-orange. Birds eat the berries and are the primary dispersers of the seeds.

The genus is notorious for its narcotic and/or toxic alkaloids and has about a thousand species worldwide. The name Solanum was in use in old herbals long predating Linnaeus. Its derivation is uncertain, but Wendy Zomlefer offers, "Presumably...derived from the Latin "solamen" meaning "quieting", which alludes to the narcotic properties of certain plants; sometimes the quieting effect is permanent." (A Guide to Flowering Plant Families, The University of North Carolina Press, Chapel Hill, 1994)