Poison Oak Toxicodendron radicans

Poison ivy is native throughout the United States and much of southern Canada and can be found in a wide variety of locations including dry or wet woodlands, thickets, valleys, clearings, fence rows, roadsides and waste ground. It can appear as a bushy, erect or trailing shrub in sunny areas or as a woody climbing vine. The climbing vines have aerial rootlets. All parts of the plant contain a toxic oil called urushiol that causes significant and long-lasting skin irritations (allergic dermatitis) in most human beings. Infection can occur from direct contact with the plant, indirect contact (e.g., dog, rake or shoes) or from breathing smoke from a fire of plant material. Some humans seem to be immune.

When it grows as a woody shrub, it can reach lengths of 6 feet; when it grows as a vine, it can reach 60 to 150 feet tall and climb high on trees, walls, and fences or trail along the ground. Birds, reptiles, deer, and amphibians can eat the plant and its berries and also use the plant as shelter. A variety of insects feed on the flowers of poison ivy too – from beetles to flies, bees, wasps, ants, and butterflies. Due to its wildlife benefits, it can be left alone in native areas with low human activity.

Poison ivy leaves are compound leaflets in groups of three, a trait that can reliably distinguish it from a number of similar native vines. The middle leaflet is longer than the outer two. It’s hard to describe poison ivy leaflets because their shape and size vary from smooth, rounded edges to serrated edges to shallowly lobed edges, but its leaflets are always in groups of three. Poison ivy leaves are shiny, bright green, and turn an attractive red or reddish yellow in the fall. The bark is dark gray and densely covered in aerial roots.

Poison ivy can be removed by either mechanical means– such as repeated mowing or pulled with gloved hands– or with certain herbicides applied to freshly cut stumps. Only use herbicide as a last resort.

Insects, Diseases, or Other Plant Problems:  Poison ivy, is the ultimate weed that no one wants. As the saying goes, “Leaflets three, let it be." Do not touch any part of a poison ivy plant. All parts of the plant contain volatile oils that can cause significant skin irritation on direct or indirect contact. Do not burn plant materials because contact with smoke from the burning materials can be just as toxic as touching the plants. Breathing the smoke can be even more hazardous.