Poison Ivy – Leaves of Three, Let it Be

By Vijai Pandian, Horticulture Extension Educator for Milwaukee, Kenosha, and Racine Counties

Summer is a great time to explore Wisconsin’s rich natural resources. When you camp, bike, or hike you may encounter diverse trees, shrubs or vines but none are as easily recognizable to “Poison Ivy” (Toxodendron radicans) with its distinct three leaflets. Poison Ivy, native to North America is a perennial woody vine but can also have variable growth habits from being upright shrub or creeping groundcover in its early stage. It is a common pesky plant found in pastures, roadsides, fence rows, wooded forests, beaches and parks.

Poison ivy has a distinct alternate compound leaves with three leaflets where the middle leaflet is slightly larger in size and attached to a short stalk. Generally the leaflets are oval shaped with pointy tips with variable margins and textures (serrated, even, lobed, shiny, dull, or hairy).  In late summer, poison ivy produces clusters of whitish berries and its seed are spread by birds through droppings.

The plant is noted for its toxic resinous oil called urushiol causing severe itch, inflammation or blisters on skin when in contact. The entire plant parts including its root, leaves, stems can secrete the urushiol oil. Generally urushiol is a colorless oil but it can have a slight tinge of yellowish in color in main stems and roots. The oil has strong adherence property and can spread through garden tools, clothing materials, boots or even pet animals that have been in contact with the plant. Urushiol can remain active even on dead plants and roots for two years and any attempt to burn the dead plants can risk in releasing the toxic vapor causing severe allergic reaction.

To prevent poison ivy injury, get a positive identification of local plants in property and mark off the section of the property that contains large population of poison ivy plants.  Young boxelder seedling (opposite leaves) and Virginia creeper (five leaflets) can be easily confused with poison ivy. Always wear a long sleeved shirt and long pants with boots when spending time in the poison ivy infested area. Isolate the contaminated clothes including gloves and boots after working in the infested area and wash it separately in hot soapy water.  Use wipes to clean gardening tools that may have come in contact with plant.

If exposed to the urushiol oil, wash the infected skin in a running cold water immediately. Avoid using complexion soaps as it tend to spread the oil on the skin.  Poison ivy cleansing products (like Tecnu skin cleanser, Poison Ivy scrubs) can help remove the oil from the skin with 4-8 hours after exposure. Magnesium sulfate can also help to detoxify the oil and ease the itching.  It is best to apply preventive lotions (like Ivy Shield, Ivy block lotion) while working in a known infested area to minimize the risk of poison ivy effect on skin.

Always wear long, thick, water proofed rubber gloves when treating and handling poison ivy plants. The use of herbicides containing active ingredients like glyphosate (Roundup) and triclopyr (Brush killer) are effective in controlling poison ivy. Spot treat the young plant on less windy days or cut the main stems of the shrub or woody vine to the ground and paint the stump with concentrated herbicide. Fall treatment is effective in controlling poison ivy. Always read the product label for its safety and instruction. Do not mix the poison ivy brush materials in to your regular compost pile. It is best to bag the brush materials, label it and trash the bag through garbage disposal. Do not burn the brush pile.  After removing the brush, clean the infested ground for any leftover poison ivy berries, leaves, stems and roots.  The oil can still remain active in the soil surface even after the cleanup and it is best to avoid exposing the contaminated soil surface by adding layers of clean wood chip mulch on the site.