Poison ivy (Toxicodendron radicans) is a plant in the family Anacardiaceae. The name is sometimes spelled “Poison-ivy” to indicate with the hyphen that the plant is not a true Ivy or Hedera. It is a woody vine that is well known for its ability to produce a skin irritant that causes an itching rash for most people, technically known as urushiol-induced contact dermatitis.
The leaves are compound with three almond-shaped leaflets. The berries (actually drupes) are a grayish-white color and are a favorite winter food of some birds. Hence the mnemonic,
“Leaves of three, let it be; berries white, danger in sight.”
The color ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall. The leaflets are 3-12 cm long, rarely up to 30 cm. Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth. In comparison, blackberry and raspberry leaves also come in threes, but they have many teeth along the leaf edge, and the top surface of their leaves is very wrinkled where the veins are. The stem and vine of poison ivy are brown and woody, while blackberry stems are green with thorns.