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.