HOW DOES YOUR GARDEN GROW?
By Kit Flynn
It’s hard to have a sense of humor about poison ivy. In fact, I have a hard time saying anything nice about this native plant as I’m highly allergic to it. However, that being said, provided we stay far away from it, it is a plant of interest. This very old plant is one that botanists believe evolved over 80 million years ago when the dinosaurs ruled the planet.
Thrilled with its brilliant fall color at a time when New World plants were the rage, John Tradescant the Younger, naming it Frutex Canadensis epimedium folio, imported it back to England in 1632. From there, it quickly joined the ivy genus, becoming Hedera trifolia Canadensis until Carl Linnaeus came to the rescue, simplifying it to Rhus radicans.
In the 1930s, botanists took it out of the Sumac genus, reclassifying it as Toxicodendron, meaning “poisonous tree.” Today Toxicodendron includes poison oak, poison sumac, cashews, mangoes, the Chinese and Japanese lacquer trees and the infamous Brazilian peppertree that is an invasive scourge throughout Florida.
Now, there are some interesting aspects of poison ivy. In the first place, it is not poisonous, nor is it technically an irritant. What makes poison ivy so uncomfortable for so many of us is its oil, urushiol, which is not a poison. Interestingly, humans are the only creatures who are allergic to it, explaining why our dogs can romp in it and we cannot—but take care to don some gloves and wash your poison ivy-exploring dog so the oil doesn’t transfer to you.
About 85% of all of us will have a reaction to it. The resulting contact dermatitis is actually caused by an attack by our immune system.
Initially, the first contact typically will not cause a reaction (the reason children under five rarely get the rash as sensitivity usually occurs between the ages of five and ten) except in those individuals who are highly susceptible to urushiol. With each contact, the sensitivity grows; the good news is that the longer the time between exposures, the vulnerability decreases in many people.
In the second place, this allergy is different from other allergies. While 85% of us are affected by urushiol, only 20% of us have standard allergies. Consequently, many of us within that 85% have no other allergies, whereas standard allergy sufferers typically will react to more than one allergen. Those in the 15% who have no reaction to urushiol may have children who are highly susceptible to it; many standard allergies carry a hereditary component.
Urushiol penetrates the skin’s surface quickly, somewhere between 10-20 minutes, so speed is of the essence to mitigate reaction. Washing the surface with a strong soap quickly helps those who are only moderately sensitive, but it does little for those who are highly susceptible. The urushiol dermatitis appears more quickly on warm days when our skin pores may be more open and our clothing reduced; perspiration also helps to spread the oil.
The old yellow laundry soaps that traditionally came into play are not recommended because, not only are they now hard to find, they are also very rough on the skin. Most experts now call for using a laundry detergent in warm water as warm water opens the skin pores. Rinsing in cold water within three minutes of contact is also advantageous—so, if you are exposed in the garden, quickly reach for that garden hose.
Urushiol remains on the plant throughout the year, even when it’s dormant or dead. This is a tenacious oil, one that can remain on clothing after laundering because it’s not water-soluble. In fact, tainted clothing after one year is still capable of causing a rash.
The rash will last 14-21 days. Calamine lotion may temporarily stop the itching, as will hot water. Prescription cortisone creams are effective if used early. One of my sons, when younger, was so sensitive to urushiol that he found the only relief was a cortisone shot. There are also barrier creams that may provide some protection for up to four hours.
Birds love the berries, gladly depositing the seeds in our garden so chances are you will come across young plants that seemingly appear out of nowhere. I use inexpensive coated gardening gloves that are excellent for pulling out these young seedlings. I then throw out the gloves as a safety measure.
There are some fallacies relating to poison ivy, so let’s get to the facts before someone gets hurt:
- You cannot get poison ivy by standing close to the plant. Urushiol is heavy. While it can be carried by smoke, it cannot be transported by wind;
- Scratching does not spread the rash. It can make the infection worse, but the oozing wounds do not carry the oil. The rash spreads because of increased contact with residual oil;
- Eating the spring leaves will not create a resistance to the effects of the oil. Only do this if you are pining for a visit to the ER (do call 911 if you experience trouble breathing or feel faint after exposure);
- Bathing does not spread the rash. The most important thing to do is to wash—and wash well—or rinse well upon exposure; and
- Rubber gloves are not recommended for handling mature plants; the only recommended gloves are leather gloves that you discard immediately after using.
To kill established poison ivy in the garden, first use a urushiol blocking cream and cover yourself with clothing (probably ones that you are willing to discard) leaving few exposed areas. You can use glyphosate during warmer temperatures or one of the commercial poison ivy killers during the cooler months. It is imperative that you do not burn it.
So, what should you do with the carcass? I called Chapel Hill’s Sanitation Department to find out; it should be placed in a yard refuse container for the crew to dispatch it in their truck. Do not leave the cut pieces lying on the curbside. Another suggestion: If you have access to goats, poison ivy is a nutritious plant they love to eat.
The one fact about poison ivy to keep in mind is this: Like the cockroach and the earthworm, it will undoubtedly survive us so learn to deal with it. After all, it has existed for over 80 million years, which is no small achievement.
After being an active member of the Durham County Extension Master Gardeners for 13 years, Kit Flynn now holds emeritus status. For five years she was the gardening correspondent for “Senior Correspondent” and shared “The Absentee Gardener” column with fellow Master Gardener Lise Jenkins. She has given numerous presentations on various gardening topics to Triangle organizations and can be reached at email@example.com.