Plant of the Week: Poison Ivy

Written by: Engineering Conservation Crew

As children, we learn “leaves of three, let it be” to remind us to avoid the shiny leaves. Though often despised by humans, Eastern poison ivy (Toxicodendron radicans) is native to the United States and sought after by many native animals and insects.

Frequently, poison ivies are placed in their own genus, Toxicodendron (from the Greek for “poisonous tree”). The entire plant is poisonous because all parts, leaves, stems, and roots, contain the irritating oil “urushiol”. Yes, that means you can get a rash in the wintertime if you come into contact with the bark! Urushiol is a colorless or slightly yellow oil and is very potent. Surprisingly, relatively few wild animals are susceptible to poison ivy and indeed, many game species, rodents, livestock, and birds consume the foliage or white, berry-like fruits

 without ill effect. The fruits of the female plants are white or greenish drupes and are an important winter food for many birds.

Poison ivy is typically a deciduous woody vine that attaches itself to trees or other objects for support, but it can take on different growth forms depending on its age and growing conditions. When growing in a tree, mature vines become thick and develop dark brown hairy holdfast growths called adventitious roots; but this does not harm the trees unlike many vining plants. This species life cycle begins as an herbaceous perennial and becomes a woody vine. Poison ivy is deciduous, turning bright red and yellow in the fall and then losing its leaves. After shedding its leaves, the vines leaf out again next spring, usually in May.

Poison ivy is considered a nuisance species in many of our public areas and parks due to its inconvenient contact effects. As such, it is generally removed for the safety of the residents. We are working to do the same on our highly trafficked public storm water land and greenways. However, this plant makes itself at home in more secluded and wildlife areas. Its benefits to native wildlife cannot be fully ignored, and finding an effective population balance for the species is always being considered. 

The Engineering Division focuses in on a Plant of the Week to raise awareness of different plants in the field that benefit our environment. The Engineering crews in the field tasked with conservation share expert insight on these plants and their benefits each week in a creative way!