Poison ivy is a toxic vine that climbs to 60 feet high, trailing or climbing by aerial roots. Sometimes it appears as a low, upright shrub.
Leaves are alternate, compound, with 3 leaflets (“leaves of 3, let it be”) that are variable in size and shape; the end (center) leaflet has a stalk ½–1¾ inches long, which is longer than the stalks on the other 2 leaflets; side leaflets have unequal sides.
Stems are light brown, hairy, with raised pores, climbing by aerial rootlets. Stems trail until they find support; lacking support, they assume an erect, shrublike posture with single stems.
Flowers May–June, with clusters 1–4 inches long on new growth of stems. Flowers are small, greenish white, and fragrant.
Fruit ripens August–November, berries in grapelike clusters, persistent, about ¼ inch across, creamy white, waxy, globe-shaped, usually smooth.