Leaves of Three, Let It Be

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It’s that time of year when I’ve been itching to be out in the yard, cleaning up and getting ready to plant. Now I’m itching, literally. Pulling out what I thought was another species of vine turned out to be Poison Ivy (Toxicodendron radicans). After about 15 minutes of pulling, I noticed 3 very small newly emerged leaves, then I spotted the aerial (hairy) roots along part of the vine. Not meaning to be out there very long I had not donned my garden gear of long sleeves, long pants, and socks. “Leaves of three – let it be. Hairy rope – don’t be a dope.” Oops!

poison IvyPoison ivy is one of the most frequent causes of skin rash among people who spend time outdoors. Some folks are not allergic, while others are somewhat highly allergic to this plant, and to poison oak and sumac. It has three shiny green leaves and a red stem and typically grows in the form of a vine. It grows fairly quickly and propagates itself by underground rhizomes and seeds. Seeds are quickly spread by birds and other animals that eat the small fruits.

The rash is caused by skin contact with the irritating oil urushiol (resin) of these plants. Smoke from burning these plants can cause the same reaction and the smoke can travel affecting folks downwind too. The oils usually enter the skin rapidly. It is rarely spread from person to person.

Contrary to popular belief, the rash does not spread by the fluid from the blisters. Once a person has washed the oil completely off the skin, the rash is usually not contagious. However, the plant oils may remain active for months on contaminated clothing, pets, tools, shoes, and other surfaces. These are now sources for problems in the future if they are not properly cleaned.

Since I didn’t immediately have a skin reaction, I mistakenly thought I got lucky. I should know better. I’m never that lucky. The fact is that the worst symptoms are often seen during days 4 to 7, although for those of us who are sensitive to it, the rash can start to show up in 12 – 48 hours and may last for 1 to 3 weeks. If you’ve encountered poison ivy plants then time is of the essence. Because the plant oil enters skin quickly, try to wash it off thoroughly with soap and warm water within 30 minutes. After 30 minutes the oils bind to the skin and are very difficult to get off with soap and water. Washing with soaps that contain oils, such as complexion soaps, can actually spread the irritating oil and make the rash more widespread. Rubbing alcohol is a better solvent for the oil than water.

Washing to remove the oils is step one. Follow this with scrubbing under the fingernails with a brush to prevent the plant oil from spreading to other parts of the body. Just think about where you unconsciously scratch! Yikes! Remove and  wash clothing and shoes that have come into contact with the plant with soap and hot water. The plant oils can linger on them. If Fido and Felix were out in an infested area, they need a bath too to remove the oils from their fur.

If you have this pesky plant at your place there are some actions you can take. For light infestations, dig up small plants. Don’t forget to protect yourself with the right garden gear. You can also repeatedly cut back the plants to ground level. Eventually they starve to death. To deal with poison oak and poison ivy chemically, use an herbicide that contains glyphosate, triclopyr, or a 3-way herbicide that contains 2,4-D amine, dicamba, and mecoprop as the active ingredient.

Often poison ivy and poison oak grow up within landscaping that we want to protect and these ingredients will cause damage to them iherbicide contact is made. To prevent this from happening, cut back the poison ivy or poison oak and spray or paint the herbicide only on the freshly cut stems or stump to control where the herbicide chemistry touches. These ingredients move into the plant through the leaves and cut stems (translocate) to eventually shut down the roots and shoots. It may require repeated applications as indicated on the product label. ALWAYS read and follow the label for your safety and success. Pesticides can adversely affect pollinators. If applicable, the label will have specific information about how to safely use the product in respect to preventing potential pesticide exposure to bees and other pollinators.

As is often the case, timing is everything and these herbicides have different schedules for best results. Poison ivy and poison oak are most sensitive to 2,4-D amine and dicamba treatments in late spring or early summer when the plants are actively growing rapidly. Triclopyr offers the best control after the leaves fully expand in the spring and before leaf color changes in the fall. Glyphosate offers the best control when applied between 2 weeks before and 2 weeks after full bloom (early summer) and should be mixed to a 2% solution.

If you are clearing a site for future landscaping the choice of herbicide matters as some products will affect new plant installations with residual chemistry in the soil, others not so much. For planned beds, glyphosate has far less soil activity (a few days) as compared with the 3-way herbicides (a few weeks) and triclopyr (several months). Glyphosate is the safest choice for spray application in existing flower and shrub beds, so long as you are careful to prevent drift to non-target plants. Glyphosate applications are much less apt to move through the soil, be absorbed by roots, and injure existing woody ornamental shrubs.

For more information, contact me at minda_daughtry@ncsu.edu or your local Extension Agent.