Poison ivy is a true generalist, appearing as a bushy ground-level shrub in open sunny clearings, a trailing plant along fence rows, or a woody vine hauling itself 60 feet or more into tree canopies on densely rooted aerial stems. Its three-leaflet compound leaves vary enormously in shape, from smooth-edged and rounded to coarsely toothed or shallowly lobed, but the arrangement of three leaflets with the center one on a longer stalk is consistent and reliable for identification. Leaves are glossy bright green through summer and turn a striking red or reddish yellow in fall, making the plant genuinely ornamental in seasons when its identity is most easily forgotten.

The urushiol oil present in all plant parts causes allergic contact dermatitis in the majority of people, and potency does not diminish with drying or burning. Contact with smoke from burning plants is particularly hazardous. Within that context, the plant's ecological role is substantial. Birds, deer, reptiles, and amphibians eat the white berries and use the dense vine growth as shelter. Beetles, flies, bees, wasps, ants, and butterflies all visit the inconspicuous green spring flowers. In native areas with low human foot traffic, the plant is best left alone, its dense seed crop and wildlife value outweighing the argument for removal.