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Division of Agricultural Sciences and Natural Resources

Leaflets of three, let it be

pests_poisonivy2.jpgSTILLWATER, Okla. – A rash, red blisters and uncontrollable itching. Those who have been impacted by poison ivy are familiar with what it can do. Those who have not should consider themselves lucky.

The best defense against poison ivy is to be able to recognize it and avoid it, said Karen Hickman, professor in Oklahoma State University’s Department of Natural Resource Ecology and Management. However, to be able to identify the plant, a short botany lesson is helpful.

“It’s important to understand the difference between a simple leaf and a compound leaf,” she said. “Simple leaves are made up of a blade and the petiole, which is the stalk that attaches the leaf to the stem. You can usually find a little bud where the stalk meets the stem.”

On the contrast, a compound leaf is made up of several leaflets along the petiole. The entire structure, from the stem to the end of the leaflets is one leaf. This is the category in which poison ivy falls.

Poison ivy is a trifoliate compound leaf and will have three separate leaflets. The two lateral leaflets will jut out off the petiole, with the terminal leaflet coming straight out.

“The old adage ‘leaves of three, let it be’ isn’t exactly accurate,” Hickman said. “Maybe adopting the idea of ‘leaflets of three, let it be’ would be better.”

The plant can grow as sparsely branched shrubs, as a shrub in a thicket, a ground cover and in vines, allowing it to climb up in trees. Poison ivy can grow in full sun, or in shade, have pale green leaves, or dark leaves and the size of the leaves can vary greatly.

Leaflets can have smooth outer edges or be very jagged in their appearance.

“Being able to identify poison ivy isn’t always the easiest thing in the world to do because of the variations in size, shape and location,” Hickman said. “But one thing you can know for sure is the plant is going to have three leaflets and it is going to itch like crazy if its oil gets on your skin.”


Sean Hubbard
Communications Specialist
Agricultural Communications Services
145 Agriculture North
Oklahoma State University
Stillwater, OK 74078
Phone: 405-744-4490
Fax: 405-744-5739

Oklahoma State University - Stillwater, OK 74078