Leon M. Lederman Science Education Center
Fermilab Flora and Fauna Virtual Exhibit

Poison Ivy

Prairie Resources - Exhibit Home

What is poison ivy?

Poison ivy (Rhus radicans L.) is a plant found in nearly every part of the United States and Canada. Poison ivy has many different forms but all varieties are of the same species. It may trail, creep along the ground, develop a thick woody stem and climb up a tree or grow as an erect shrub up to six feet tall. Every part of the poison ivy plant can cause an allergic reaction.

Do we have poison ivy at Fermilab?

Yes! You will find poison ivy in most of the woods and some of the open fields at Fermilab. To avoid contact with the smaller plants stay on the paths. To avoid contact with the woody vines, look before you touch the trunk of a tree. Roads and Grounds controls poison ivy with herbicides when it invades areas that people use frequently.

How do I identify poison ivy?

The highly variable leaflets are glossy or dull, hairy and toothed, lobed, or without teeth. Poison ivy will have three leaves with one pair of lateral leaflets and one longer terminal leaflet. Small green/white/yellow flowers that turn into small whitish berries can be seen during the months of June and July in this area. The three leaflets turn to a crimson red color in the fall. When growing as a vine, attached to a tree, look for the hairy stem. If the vine is hidden, be careful because the leaves can look as though they belong to the tree.

Where does poison ivy grow?

Poison ivy is a ubiquitous plant, equally likely to occur in dry or wetlands. Poison ivy is often misidentified because the leaves resemble many other plants. Once an allergic reaction has been experienced, a person is inspired to develop the observational abilities of a botanist to avoid the plant.

What causes the irritation?

All parts of the plant contain an oily resin containing urushiol. Contact with urushiol can cause minor to severe dermatitis, consisting of an itchy rash and blisters. This can be very serious especially in the oral and nasal passages. The urushiol can penetrate the skin in minutes and cause a rash in 12 to 48 hours, blistering within a few days with severe itching, followed by crusting and scaling, usually clearing up in 10 days.

This information cannot replace the advice and assistance of medical personnel.