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FLORA FACT

Incredibly Itchy Ivy

Learn to identify this noxious plant so you won’t need an ocean of calamine lotion.


Most of us learn about poison ivy the hard way. A day or so after being outdoors, an itchy rash appears and then keeps getting worse, forming blisters and swelling. Somehow, somewhere we got into poison ivy. The misery is memorable.

Urushiol oil, found in the plant’s sap, is the villainous substance that wreaks havoc with our skin. Even clothes or pets that rub against the plant can transfer the urushiol to you and cause an outbreak. The urushiol oil can stay active on any surface — dead plants, garden tools, fishing poles and more — for up to five years, just waiting to irritate. However, you can’t “catch” a poison ivy outbreak from someone else’s outbreak; it’s not contagious.

That itchy discomfort provides great incentive to make poison ivy one of the first plants we learn to identify out in the natural world.

Of course, we all learn to look for three leaves on a stem, but many plants can fit that description. Size isn’t a good indicator because the plant can look very small at first, creeping along the ground, but it can also climb high up trees, walls or fences, even tree trunks. There are no thorns, just tiny hairs along the vine.

Poison ivy grows almost everywhere in Texas (except localized in the western Panhandle) and in almost any type of environment. All parts of the plant are toxic in all seasons, but the oil is most active in summer. Burning leaves are particularly dangerous because the toxin is carried in the smoke and can cause serious respiratory damage if inhaled.

Despite its name, poison ivy’s not a true ivy but rather a member of the cashew and pistachio family (Anacardiaceae). The poison ivy plant flowers from May to July. Berries form after that — small white or cream-colored balls drooping from the leaf axils. Poison ivy is commonly eaten by many animals, and the seeds are consumed by birds.

Always remember “leaves of three, let it be” when trying to determine if a plant is poison ivy or one of these other troublemakers.

Photo © Darren4155/Dreamstime.com

POISON OAK

A woody vine or shrub with three lobed leaflets that look like oak leaves and green berries that ripen to white. The branches are smooth, without hairs.

Photo © Norman Melvin, hosted by the USDA-NRCS PLANTS Database

POISON SUMAC

Also known as thunderwood, poison sumac can grow up to 25 feet tall; each leaf contains seven to 13 leaflets with the odd one at the tip. White berries (the good kind of sumac has red berries) are found in clusters.


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