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Plagued with Poison Ivy?

September 18, 2002

While doing some yard work, you come across a mysterious and uninvited viny plant. You reach for it and suddenly, that old familiar rhyme, "leaves of three, let it be," rings in your mind, so you quickly pull away. What should you do next? How do you remove something you shouldn't touch? The short answer is very carefully; I'll cover the long answer in a moment.

First, are you sure you have poison ivy or could it be something else? Be aware other plants, such as box elder, that also have "leaves of three" Many also mistake other vines such as Virginia creeper and trumpet creeper for poison ivy. However, when unsure, it's certainly safest to avoid touching any poison ivy look-alike.

Poison ivy (Toxicodendron radicans) is a perennial that can grow as a woody vine or shrub. The leaves grow alternately up the stem. What is certain is that the leaves are compound--made up of three large, palmately borne leaflets. What is not always certain is the appearance of the leaflets. Two plants may look very different. Leaf margins may be smooth or serrate, the leaf surface may be glossy or dull, leaves may be lobed or unlobed, and color may be almost any shade of green. A typical shape is that of a mitten, but leaf shape may vary.

All of this creates much confusion, for me at least. But once all those variable leaves have dropped in the autumn, one of the best ways to quickly identify a woody vine as poison ivy is to look for the presence of numerous aerial roots on the vine. These are reddish brown and give the vine a fuzzy appearance. You may also see the fruit, which are produced in late summer, but which can persist throughout the winter.

White flowers appear usually in May and June; and small, round, greenish to grayish white, berrylike drupes soon follow. Birds feast on this fruit and readily disperse the seed. Furthermore, poison ivy also reproduces by creeping root stocks and by stems that root where they contact the soil. Consequently, this plant is found in many parks, landscapes, woodlands, and wetlands. It thrives under a variety of conditions.

In the fall, leaves turn a gorgeous red in Illinois. In fact, this plant has been imported into a few countries for this reason. Personally, I don't think it's that pretty, considering the itching part. Year-round, all parts of the plant except the pollen contain a resinous compound, or "oil," that causes itching and blistering on the skin of most people. Animals are less sensitive to this oil, but if you are sensitive to it and pet your dog or cat that has been rolling around in it, watch out! If you are washing clothes contaminated with poison ivy, be aware the oil may still be present (which can give you a rash). Don't worry about touching someone else's or your own rash because the oil is the only cause of the irritation. You can't get a poison ivy rash from someone who already has the rash. Also, smoke from burning poison ivy plants can cause irritation in some people.

Poison ivy is difficult to kill, and you may need to be persistent with your control efforts. Plants may be physically removed, including the roots. However, resprouting is likely to occur if any underground parts are missed. Also, this may be too close for comfort for those who are allergic to poison ivy.

Another method that involves a little less contact with the plant is to cut off the plant at its base and treat the stump with a herbicide such as triclopyr (Ortho Brush-B-Gon, Garlon, etc.) or imazapyr (Arsenal, Stalker, etc.). It's helpful to flag the area so you can easily check periodically for regrowth. If regrowth occurs, make a second herbicide application.

Waiting until the foliage dies down before removing it could decrease your risk of getting a rash. But keep in mind, the oil is still found on the plant a long time after it dies. If you can't find the base of the plant or can't get to it easily, foliar applications can be made with products labeled for this use that contain the active ingredients mentioned or dicamba (Banvel, etc.). However, if poison ivy is covering other plants, those plants are likely to be injured or killed by the herbicide.

Another consideration is soil mobility of herbicides, especially if roots of desirable plants are nearby. In this situation, glyphosate (Roundup, etc.) would be a better choice. Control can still be achieved, but soil mobility is not an issue because glyphosate is tightly bound to soil. With any product, complete control may not be achieved for a few years, and multiple applications may be necessary. Remember always to read and follow the product label.

These active ingredients may also be written on the product label as:

triclopyr, [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid

imazapyr, ()-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-

3-pyridinecarboxylic acid

dicamba, 3,6-dichloro-2-methoxybenzoic acid

glyphosate, N-(phosphonomethyl)glycine

Author: Michelle Wiesbrook


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