JIM BOUGHT his first house last summer. He left the office one Friday saying he was going to spend the weekend weeding his garden for the first time. Jim never made it in that Monday, nor did he come for the next two weeks. The weeds turned out to be poison ivy. Within 24 hours he was one red rash, head to toe.

If you managed to get this far into summer without coming across this poisonous week, chances are your grass and gardens are not infested with it.

But it could be lurking in your bushes, waiting to spring on the unaware.

Look for:

A three-leaf plant with smooth, glossy upper surface. It often grows as a vine in moist, shady spots. In the fall it has white berries and red leaves. The plant is most common in the eastern and central portions of the United States.

"Get the poison ivy plant before it gets you," advises extension agent Bruce Whiton of the Alexandria extension service. He says there are two ways to do this.

"If the ivy is among the grass on your lawn, use a broad spectrum weed killer, also known as a herbicide." It should contain 2,4-D and dicamba. The herbicide, Amitrol, may also be used. "Simply put," explains Whiton, "these checmicals combine to cause the plant to grow itself to death. They act as a plant hormone, speeding up growth, the roots can't keep up and eventually the plant burns itself out."

According to Whiton the entire process takes a few days.

Follow the directions on the label. Use on a still day to avoid the spray drifting to other plants. Painting the herbicide on the plant leaves is suggested by the pamphlet, "Poison Ivy Allergy," published by the National Institute of Allergy and Infectious Diseases. Unlike pesticides, herbicides require no watering for absorption.

"Howver," adds Whiton, "poison ivy doesn't always grow in easy-to-reach spots such as your lawn. Sometimes you find it in the midst of your garden, growing among your favorite azalea bushes.

"In this case," he says, "you can't use a herbicide, since it will kill the azaleas as well as the poison ivy. Instead, put on a long sleeve shirt and with rubber gloves pull out the ivy, roots and all."

Once you have taken away the ivy -- you should remove it from your lawn as well, says Whiton -- place it in a bag, seal it and deposit it in the garbage. Dead ivy should not be left around or buried since it still carries the active chemical urushiol in the sap of the plant. Urushiol is the ingredient that causes the rash.

After removing clothes, wash them carefully -- separately from your other clothes. Wash the surface of your rubber gloves with soap.

"Above all," Whiton says, "don't burn the poison ivy plant. The smoke you inhale can give you just as bad a rash -- sometimes worse."

Although you may be exposed to the poison via your nose, throat or lungs, you will not get the infection anywhere except on your skin, says Dr. Melvin Elgart, chairman of dermatology at George Washington University.

Exposure occurs, states the pamphlet "Poison Ivy Allergy," when you rub or crush the plant or leaf, allowing the urushiol to touch your skin. You can also contract the allergy by touching the fur of a pet that has rubbed up against the plant.

This year, before Jim started putting about in his garden, he had his neighbor drop by and point out the poison ivy while Jim sprayed.