Extension Educator, Horticulture
You may not be able to tell an artichoke from an aster, but poison ivy is one plant you should be able to pick out of a line-up.
Poison ivy is a woody perennial plant that may grow dwarf and erect or vine through trees or along fences. The 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.
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.
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.
The intense irritation and blisters follow contact. The blisters may break and release a liquid, but the liquid cannot cause more blisters. Symptoms usually appear within 24 hours, but may appear in a few hours or a few days.
Some people are more susceptible than others. The amount of poison available in the plant can also vary. A person can become less immune with repeated exposures. Despite popular myth, under no circumstances should you eat a leaf in order to promote immunity. Severe gastric irritation and even death can result.
According to the booklet Pesky Plants by Thor Kommedahl, the reaction of the poison with the skin is nearly instantaneous. However, immediately washing with strong soaps or rubbing alcohol can remove any excess poison that might be transferred to other parts of the body. I like to take moist towelettes when I'm hiking just in case.
Wash any exposed clothing in hot soapy water and not with the family wash.
There are three basic methods for controlling poison ivy in a landscape. Any control measures require proper protective clothing.
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. The poison ivy then can be neatly disposed of in its bag.
2) Cut vine and pull it out of existing plants 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 as spray dries may be needed.
Remember there are no herbicides that will selectively control poison ivy and not harm landscape plants. Any herbicides must be used with care so as not to contact desirable plants. Do not apply on windy days or if temperatures are above 85°F. Be sure to read and follow all label directions.
Herbicidal soaps such as SharpShooter work well on small seedlings, but older plants will regrow from the roots. Glyphosate such as Roundup or Kleeraway is most effective when applied two weeks on either side of full bloom in early summer. Herbicides containing triclopyr can also be effective.