September 2011
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Avoiding Poisonous Plants


Beware of those poisonous vines while working in the yard this summer. Each year many Alabamians come in contact with poison ivy, poison oak and poison sumac while in the outdoors, but it is not only summer when you have to be careful, so always be on the lookout. Even in the winter when the vines look brown and dead, they still contain oils that will cause allergic reactions. These plants can cause a great deal of discomfort, itching and pain from contact on the skin and even greater if the oils get in your lungs or eyes. So never burn these vines as the oils can get in the air and be inhaled.

All three of these poisonous plants are easily found throughout the Southeast, but they look very similar in appearance and are often confused with each other and other plants like Virginia creeper, box elder or fragrant sumac, all of which are nonpoisonous.

Poison ivy is often found climbing high on trees, walls or fences or trailing on the ground. This woody vine has hairy-looking aerial roots and can grow to more than 10 feet tall, said John Everest, Extension weed scientist of Auburn University.? All parts of the plant are poisonous and poison ivy always has three leaflets. Flowers and fruit form in clusters on slender stems attached to the leaf limbs. Poison ivy has toxic oil in the stems and leaves that many people are highly allergic to and develop a rash. The rash usually starts with itchiness and swelling, followed by a reddish inflammation of tiny pimples. The rash can vary in severity from person-to-person and can begin as early as an hour after contact or up to five days after contact. The oil can even be transmitted from a pet’s fur or from smoke of burning poison ivy.

Poison oak is very similar to poison ivy, but it does not climb. Its leaves are thicker, are a dull green and are hairy on both sides of the leaves. Poison oak is found in dry, sunny sites in woodlands, thickets and old fields.

Poison sumac is a shrub and can grow to 25-feet tall. Leaves are 7 to 15 inches long and have 7 to 15 leaflets to a central stem, with one leaflet at the end of the stem. It is found mostly in swamps or moist bottomlands. Poison sumac also has ivory or white berries forming clusters. Same as the poison ivy, never burn these plants and poison oak and poison sumac also have toxic oils that can cause an allergic rash on the skin.

All of these irritating plants range in appearance as leaf shapes will vary even on the same plant and they will also vary in form from rough, woody vines to erect woody shrubs or trailing shrubs running along the ground. Never base your identification on one or two leaves, but look at the overall plant and many leaves and compare size and shapes to determine the plants’ identity and, if ever in doubt, leave it alone.

May and June are the best times to apply control measures to these poison plants, but it can be done any time of the year. Spraying the foliage with products listed with the active ingredient glyphosate (sold under trade names like Roundup® or Kleenup® and others) is recommended. To kill poison ivy on trees, cut the vine right above the ground, then treat any leaves coming from the vine on the ground with Roundup®. More than one application may be necessary, but eventually this herbicide will kill the roots and prevent sprouting. Always follow directions on the label when using herbicides. Glyphosate will kill almost any plant when it comes in contact with the green plant tissue and does not remain active in the soil.

To prevent these plants from poisoning your summer, become familiar with how the plants look and avoid them. If you come in contact with one of the plants, wash your skin with strong soap and hot water immediately, and remove and wash all clothes, including shoes and socks in a strong detergent and warm or hot water. Also, keep your hands away from your eyes, mouth and face.

If you develop a rash, don’t scratch it. You can apply calamine lotion, zinc oxide ointment or a paste made with baking soda and water to the rash. If these measures don’t work, call your doctor.

Some people have severe allergic reactions to these plants and can have swelling in the throat, breathing problems, weakness, dizziness and bluish lips. Some people even fall into unconsciousness. If any of these reactions occur, seek emergency medical care.

SOURCE: Dr. John Everest, Extension Weed Scientist, Alabama Cooperative Extension System