Blog

Aug 27, 2023

How can I tell if a plant is poison ivy or poison oak or poison sumac?

Poison ivy, poison oak and poison sumac can make for an uncomfortable summer or fall. If you have ever experienced the blisters, swelling and intense itching of even the briefest of encounters, then

Poison ivy, poison oak and poison sumac can make for an uncomfortable summer or fall.

If you have ever experienced the blisters, swelling and intense itching of even the briefest of encounters, then you can appreciate these plants’ capabilities. Above all other means of defense against contact, avoidance should be your priority. But to avoid these plants, you must first be able to recognize them.

“Leaves of three, leave it be” is more than a childhood rhyme, it is a great identification tool as well. Poison ivy develops compound leaves consisting of three leaflets. The leaflets will be two to four inches long with pointed tips and a tapered base. Leaves may be smooth or hairy, glossy or dull and vary in color to yellowish-green to reddish-green.

Leaves of poison ivy are arranged alternately on the stem. Sweet-smelling, yellowish-green flowers appear in cluster in early summer and small white, waxy berries develops in the fall. Poison ivy spreads to cover areas by underground runners and seeds and can tolerate sunny or shady conditions. It may grow as a woody shrub or a slender woody vine running along the ground and climbing up trees and shrubs.

As a vine, it produces “aerial roots” which help it attach to trunks and give the vine a ‘fuzzy’ appearance. Poison ivy is most often confused with Virginia creeper, a non-poisonous plant with five leaves.

Poison oak looks similar to poison ivy but it does not climb. It has fuzzy, multi-lobed leaves that are thicker than Poison Ivy leaves. The leaves are a dull green and hairy on both sides of the leaves. The stem has no aerial roots. Poison oak prefers dry, sunny sites in woodlands, thickets and old fields.

It would be unlikely that you would encounter poison sumac in your backyard without noticing it. This poisonous plant is a shrub that can grow to 25 feet tall. The leaves are 7 to 15 inches long, pinnately compound with five to 13 leaflets per stalk. It is primarily found in swamps or moist bottomlands. Poison sumac has sweet-smelling flowers in the spring and has bright red and yellow foliage in the fall. Unlike many look-alikes, poison sumac has cream-colored berries in the fall.

Avoidance of these plants is not always practical, especially when they are growing in your flower beds. Cultural and chemical controls may be necessary in these situations. Hand-pulling poison ivy is most effective when the soil is moist. Roots should be dug out completely since regrowth can occur from any root portions left behind.

Wear gloves and long sleeves when pulling this plant and wash your clothing after you finish. Run a rinse cycle after washing your working clothes to prevent contaminating other clothing. If you are highly allergic to poisonous plants, do not attempt cultural control. To eliminate vines, sever the vine at the base and pull it from the tree.

Use a herbicide, such as Roundup, Spectracide’s Brush Killer Concentrate or Ortho’s Brush-B-Gone, to treat the regrowth. These chemicals can also be applied to non-climbing poison ivy and poison oak. Caution should be used around desirable plants since damage can occur by drift or absorption through roots.

In areas where favored plants are numerous, you may want to paint the chemical directly onto the leaves of the poisonous plant to avoid contacting other plants. Chemical treatments should be applied when plants are actively growing, however repeat applications will likely be necessary. Read and follow the herbicide label instructions. Burning is not a recommend method of eradication. During burning the soot particles can carry oils from the poisonous plants. Contact with the smoke can result in severe cases of poisoning.

The rash caused by poison ivy, oak and sumac is the direct result of contact with an oily toxicant within the plant. The plant must be crushed or broken to release these oils. If this area is touched by your hand, you can spread it by touching to other parts of your body. Because it is sticky, it can also be spread on garden gloves, clothing, golf balls or pets.

The rash cannot be transmitted by touching one of the blisters. Rash intensity varies from person to person and may take up to five days to appear after contact. Apply calamine lotion, zinc oxide ointment or a paste made with baking soda and water to rashes or contact your doctor. People who think they are not affected by poison ivy should know that the first exposure to the plants oils does not produce a reaction. It often takes multiple exposures to develop sensitivity and see symptoms, so continue to use caution.

P. Andrew Rideout is the UK Extension Agent for Horticulture and can be reached at [email protected].