Extension Educator, Horticulture
Weeds are good at their job. Through heat and drought weeds are doing well. Poison ivy is a native plant relegated to weed status in our landscapes. It is a stealthy, quick-change-artist of a weed as it grows in several forms. As a woody stemmed perennial poison ivy may grow dwarf and erect (almost shrub-like) or vine through trees or along fences.
You may not know an artichoke from an aster, but poison ivy is one plant you should be able to recognize. "Leaves of three – Let it be." Poison ivy leaves are alternate on the stem and are divided into three oval shaped leaflets which are pointed at the tip, tapered at the base and may be lobed or toothed. The terminal leaflet is longer stalked than the two side leaflets. In the spring the leaves are tinged in red and in fall often have a striking red color.
Poison ivy has small yellow-green flowers in late May to July. The fruits are white berries, which the birds eat. New plants often appear on fencerows where birds sit. Poison ivy is often confused with Virginia creeper which has five leaflets and blue berries. Virginia creeper is sometimes mistakenly called poison sumac or poison oak which are found in just a few counties in Illinois.
The poison in poison ivy is found in roots, stems, leaves, flowers and fruits. The stems can be a problem even in winter. Infection occurs from contacting broken parts of the plant, but can also occur from handling infected clothing, shoes or even petting dogs. Poison ivy should never be burned.
Here are three alternative methods for controlling poison ivy in a landscape. Always use proper protective clothing or find a volunteer with immunity.
1) Grubb or hand pull small vines when the soil is wet. With small plants place a bread bag over your hand, pull up the seedling and fold the bag over the seedling, then the poison ivy can be neatly disposed of in its bag.
2) Cut vine then paint herbicide on the cut surface of the remaining stub or treat new shoots that emerge with an herbicide to kill the roots.
3) Treat the leaves with an herbicide, which may mean painting individual leaflets to avoid contacting the landscape plants. Covering desirable plants during application and until spray dries may be needed.
Remember there are no herbicides that will selectively control poison ivy and not harm landscape plants if the herbicide contacts the stems or leaves of desirables. Do not apply on windy days or while temperatures are above 85 degrees F. Be sure to read and follow all label directions. During hot dry weather herbicides may not be as effective, therefore reapplication according to label directions may be needed.
Herbicidal soaps such as SharpShooter work well on small seedlings, but older plants may regrow from the roots. Glyphosate such as Roundup or Kleeraway is effective when applied 2 weeks on either side of full bloom in early summer. Commercially available brush killers containing triclopyr or combination of herbicides seem to be most effective.
In addition to poison ivy lurking in the landscape other plants such as Queen Anne's lace, wild parsnips, poison hemlock, and cow parsnips can cause a hypersensitivity to the sun. In some people the reaction can occur within hours of exposure to the plant and sun as itching, burning, red spots and/or large blisters. That's the catch – with some plants the reaction requires exposure to the sun. Be very careful when mowing ditch banks or weed whacking. Wear long sleeves and gloves. In addition after completing landscape chores, immediately wash skin with soap and water. Also wash all clothing in hot soapy water and not with the family wash. For answers about plants and skin reactions, contact your physician.