Monday, May 31, 2010

Poison ivy (Toxicodendron radicans)

Toxicodendron radicans – Eastern Poison Ivy or Poison Ivy – the plant we love to hate. Poison ivy grows widely in this area. It causes contact dermatitis in most people. Symptoms include inflammation and itching in mild cases and rashes and lesions in more serious cases. Thus, it’s important plant to recognize and avoid.

Poison Ivy is recognized by it’s characteristic trifoliate leaves. However, there are a variety of plants that, superficially, look like Poison Ivy. Although I've lived here for more than 20 years, I approach any plant that looks remotely like Poison Ivy with caution until I’m sure it’s not Poison Ivy and I avoid any plants that I’m unsure about.

I knew that Poison Ivy bloomed - I'd seen pictures. I’ve been looking for blooming plants for many years but it is only this year that I’ve found them both at Fort Yargo State Park and at home.

New leaves. They are among the first plants to emerge each year – still in the winter. Their leaves are shiny and often with a red tinge, possibly due to the cold temperatures. The plants are easy to recognize when the leaves are shiny.

When plants develop in warm weather the initial leaves are shiny and green. These plants have re-grown within a week after being mowed back to bare earth by the local power company.

The plant is a vine and spreads over the ground. The smaller leaves still show some sheen but the larger leaves are matte.

Stems may develop adventitious roots. This plant was growing over boulders.

A cluster of flowers on a vine that has climbed a tree. The flowers were hidden under the leaves and I didn’t see them at first. This photo also shows the hairy vines that are characteristic of Poison Ivy. It's a good rule to avoid any vine - particularly one with hairy stems - growing up a tree. (BTW, I used a stick to hold back the leaves while I photographed the flowers).

A closer view of the flower cluster

This plant looks as if it is supporting itself but it has grown up a tall tree stump. The entire area of lighter green in the foreground belongs to one plant; the stem is 2 to 3 inches in diameter.

A close view of a cluster of flowers on this plant. This flower cluster is much denser than the cluster that developed on the plant growing in the shade of the tree

Close ups of individual flowers and buds; these are about 1/4 inch in diameter.

Toxicodendron radicans
(Eastern Poison Ivy) is native to the United States. It grows in the eastern United States and Canada, as well as in Arizona.

Click on an image to view a larger image

Distribution Map:

- United States Department of Agriculture Plants Database: Toxicodendron radicans (Eastern Poison Ivy)

University of North Carolina Herbarium: Eastern Poison Ivy (Toxicodendron radicans)

Identification resources:

-Southeastern Flora: Poison ivy (Toxicodendron radicans)

- Native & Naturalized Plants of Georgia and the Carolinas: Eastern Poison Ivy (Toxicodendron radicans)

- Wikipedia: Toxicodendron radicans

Related posts:
- 2010: Year Of The Wildflower


Philip said...

An interesting question here does poison Ivy effect other animal life like Birds etc. in the same way it effects Humans with a rash or must it have contact with the bare skin first ?

JSK said...

Hi Phillip. I didn't have any idea but decided to Google it. According to the website (, both birds and animals eat it without any ill effects. In fact, they suggest that goats can be used to graze and control it.

I also suspect that my cat was responsible for some of the early encounters I had with poison ivy. I think she came in with it on her claws and transferred it to me when she kneaded my arm. I had had no other possible contact with the plant.