bittersweet, name for two unrelated plants, belonging to different families, both fall-fruiting woody vines sometimes cultivated for their decorative scarlet berries. One, called also woody nightshade (Solanum dulcamara), is an Old World plant now naturalized in North America, belonging to the family Solanaceae (nightshade family). The twigs and stems are occasionally used medicinally for a narcotic poison similar to belladonna. The more popular bittersweet (Celastrus scandens), a plant of the family Celastraceae (staff tree family), grows in thickets from Maine to North Carolina and W to Nebraska. Its berry is surrounded by an orange-yellow capsule. Both bittersweets are classified in the division Magnoliophyta, class Magnoliopsida. S. dulcamara belongs to the order Polemoniales, family Solanaceae. C. scandens belongs to the order Celastrales, family Celastraceae.