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Leaves of Three, Let It Be

Written by Rhonda Ferree, retired horticulture educator

Are your summer outings followed by days of itching discomfort? Knowing more about poison ivy and how it grows might help you avoid rash problems later.

Remember the old adage, Leaves of Three, Let It Be! Poison ivy grows in various locations and many different environmental conditions. It is in fencerows, under trees, and in ornamental shrub and perennial plantings, probably seeded through bird droppings. When growing among desirable plants, poison ivy is a challenge to control.

A member of the sumac family, poison ivy (Rhus radicans) has leaflets in threes. This means that one leaf is made up of three smaller leaflets. Leaflets usually have smooth edges with a few indentations. Although sometimes bushy and erect, poison ivy typically creeps in and around plants and up trees or structures. It has very small green flowers in the late spring and early summer, which develop into gray or whitish berry-like fruit. The fruit is an important food source for much wildlife.

I have done numerous poisonous plant programs and am surprised how few people can recognize poison ivy. Even more surprising is how many people think that Virginia creeper is a poisonous vine. In fact, many people think Virginia creeper is Poison Oak. This is just not true. Poison Oak has much smaller leaflets with rounded edges and only grows in the western states, not in Illinois. Virginia Creeper (Parthenocissus quinquefolia) is often confused with poison ivy, however Virginia creeper has leaflets of five, not three, and is not considered poisonous.

Several herbicides are available to control poison ivy, but they all will harm other plant vegetation, so care is needed. To control poison ivy in a landscape setting three methods may prove successful: (1) grubbing or hand pulling the vine when the soil is wet; (2) severing the main vine and pulling it out of the existing vegetation, then treating new shoots that emerge with an herbicide to kill the roots; and (3) treating the foliage with an herbicide, which may mean painting individual leaflets to avoid contacting landscape plant foliage.

Which herbicides work? Glyphosate (e.g. Roundup) is most effective when applied two weeks on either side of full bloom, in early summer. Repeat applications of Roundup may be required to maintain control and fall treatments must be applied before leaves lose green color. Other homeowner formulations are available and usually say "Poison Ivy/Oak" in the name somewhere. These formulations typically contain the active ingredient triclopyr.

If you think that you have been in contact with poison ivy, it is important to wash yourself and your clothing right away. Plenty of plain old soap and water helps remove the sap from both skin and clothing. If a rash does develop, follow doctor recommendations to relieve the itching. And if the rash is severe – or it affects the mouth or other sensitive areas of the body- seek medical attention immediately.

Poison ivy rashes certainly are not fun to endure, however I fully believe that enjoying the great outdoors is worth the risk. Go out and enjoy nature this summer, but stay away from the "leaves of three."



As horticulture educator, Rhonda Ferree inspired citizens in local communities to grow their own food and improve their home landscapes. She focused on high quality, impactful programs that taught homeowners how to create energy-efficient landscapes using sustainable practices that increase property values and help the environment.

After 30 years with University of Illinois Extension, Rhonda retired in 2018. She continues to share her passion for horticulture related topics as “Retro Rhonda” on social media.

ILRiverHort is a blog that helps people connect to nature and grow.