Bridge Gardens’ Weed of the Month | Eastern Poison Ivy (Toxicodendron radicans)
November 14, 2023
By Rick Bogusch
This infamous, dreaded native can be found throughout eastern North America and also in Asia. Usually a vine, with the potential to climb 75 feet up a tree, it also grows as a trailing vine and ground cover. Vines attach themselves to tree trunks, wooden fences, masonry walls and other surfaces with numerous hairy aerial rootlets. Old vines can be 3 inches or more in diameter and heavily fringed on both sides with these rootlets. Horizontal fruiting branches, sometimes 5 feet or more long, emerge from the vine and are easily mistaken for tree branches.
Best identified with this common adage "leaves of three, leave them be," poison ivy leaves have 3 shiny, toothed leaflets and are a common means of identification, as are those aerial rootlets. In autumn, leaves turn a brilliant scarlet. Flowers bloom from May to July. Small and hidden by the leaves, they provide food for many species of bees, native and introduced. In late summer and autumn, they mature into clusters of grayish-white berries relished by birds and other wildlife.
Poison ivy is usually found growing along woodland edges and in fields adjacent to woods. It is more common now than before colonization of North America began. Developed locations next to undeveloped land created the favorable “edge” conditions preferred by poison ivy and allowed it to spread far and wide, especially in the suburban areas of southern New England, the Mid-Atlantic and the Southeast.
As climate changes, poison ivy is expanding its range into areas with cold winter temperatures, like central New York. At the same time, it is also producing more of its toxic element, urushiol, and becoming more potent. Exposure to this chemical is the cause of the itching and the serious, sometimes painful rashes most of us have experienced. Research has shown that urushiol production has been stimulated by increased amounts of carbon dioxide in the atmosphere and has doubled since the 1960’s.
Poison ivy is tough to eradicate and control, especially without use of herbicides. After donning layers of disposable gloves and protective clothing, you can easily pull or dig young plants. Cut older vines at the base and remove the top 8-10 inches of roots. Most important, never burn poison ivy, as the smoke is a powerful, dangerous irritant of the throat and lungs. Dispose of vines on brush piles, not compost piles, or in trash bags.
Rick Bogusch
Garden Director, Bridge Gardens
rbogusch@peconiclandtrust.org