Poison ivy

There are numerous subspecies and/or varieties of T. radicans, which can be found growing in any of the following forms, all have woody stems: as a trailing vine that is 10–25 centimetres (3.9–9.8 in) tall, as ashrub up to 1.2 metres (3 ft 11 in) tall, as a climbing vine that grows on trees or some other support.
The deciduous leaves of T. radicans are trifoliate with three almond-shaped leaflets. Leaf color ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall; though other sources say leaves are reddish when expanding, turn green through maturity, then back to red, orange, or yellow in the fall. The leaflets of mature leaves are somewhat shiny. The leaflets are 3–12 cm (1.2–4.7 in) long, rarely up to 30 cm (12 in). Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth. Leaflet clusters are alternative on the vine, and the plant has no thorns. Vines growing on the trunk of a tree become firmly attached through numerous aerial rootlets. The vines develop adventitious roots, or the plant can spread from rhizomes orroot crowns. The milky sap of poison ivy darkens after exposure to the air.