YOUR GARDEN — Plant Information

Pests, Problems, and Diseases

Poison Ivy

(Toxicodendron radicans)

How to Identify Poison Ivy
Poison ivy takes many forms, so it is particularly important for parents, camp counselors, hikers, gardeners and anyone who enjoys the natural world to become familiar with its characteristics in all seasons. It can grow as a sprawling ground cover, a woody shrub or a woody vine climbing fences, trees, telephone poles, or even buildings in more rural areas. Urushiol, the resin responsible for producing allergic reactions in people, is present in every part of this plant and can persist for years, even on a dead vine.

Often found on disturbed sites, poison ivy is frequently seen at the edge of woodlands and roadsides, hugging sand dunes, and creeping along residential alleys, forest preserves, and campsites. It is an opportunistic plant and will spread if not checked.

Leaves
"Leaves of three, let them be" is a good rhyme for small children to remember since a key identifying feature of poison ivy is its compound leaf composed of three leaflets. Each leaflet can be between 2 and 4 inches long, with pointed tips. The middle leaflet is generally the largest of the three. The leaflets might be shiny or dull (or a combination of the two), and the margins of the leaflets might be toothed or smooth. These variable characteristics can frustrate those looking for quick identification marks. The leaves grow alternately on the plant’s stem as opposed to plants whose leaves appear exactly opposite each other on plant stems. In spring, the emerging leaflets often take on a shiny reddish-green cast, and in fall the plant will turn scarlet if grown in full sun. A plant often confused with poison ivy is Virginia creeper. While these two ground covers/vines share some features, the primary difference is that Virginia creeper’s leaves are composed of FIVE leaflets, not THREE, as found in poison ivy.

Stems
When growing as a vine clinging to a support, the main woody stem will produce hundreds of tiny aerial roots, giving it the appearance of a "fuzzy rope." As a rambling ground cover, the stems usually remain greener and less woody.

Flowers & Fruit
In late spring to early summer, the plant produces clusters of insignificant greenish flowers located in the axils of the leaves. As summer progresses, these flowers develop into grayish-white waxy berries with lines on their surfaces. Each berry is less than 1/4 inch in diameter. If a plant is missing its berries, it might be because birds often feed on them.

How to Control Poison Ivy
There are several methods available to gardeners, depending on the size of the plant and the time of year it is discovered. Use caution and wear protective clothing, shoes and several pairs of gloves since the urushiol will remain on any clothing it contacts.

CUTTING

In spring, cut the emerging ground cover shoots to the ground. Repeat this process as soon as new shoots are discovered, and continue cutting until the plant no longer produces shoots. Cutting shoots is most effective when they are just beginning to sprout. When cutting a woody vine, sever the vine close to ground level and paint the stump with an approved herbicide. Multiple applications over a period of time are often necessary to kill the vine.

DIGGING

When the soil is moist is the best time for careful grubbing, or digging, of young ground cover plants. Take care to remove as much of the root system as possible, as well as all above-ground growth. Since this process brings the gardener very close to the plant, great care must be taken not to spread the resin on clothing, tools, gloves or garbage bags.

HERBICIDES

Early in the season, emerging leaves can be painted or sprayed with an approved herbicide. Spraying will cause drift and is not recommended if the poison ivy is growing in the middle of a garden area or is attached to a tree or shrub. Either paint the leaves or the cut end of the vine’s stump to isolate the herbicide.

The Chicago Botanic Garden's Plant Information Service (847) 835-0972 can provide gardeners the names of currently approved hebicides. It is the responsibility of the gardener to use any product exactly as the directions specify, since many of these products are nondiscriminatory and can damage or kill nearby crops, plants, trees, or other vegetation they contact.