Friday, September 10, 2010
Another article published: That Dreaded Weed!
Hey hey, that was fast! My most recent article, this time on native wildflowers, appears in today's Franklin Country Gazette. Here is the previous article. . .
That Dreaded Weed, Poison Ivy
I sometimes wonder how often the previous owners of my house suffered from rashes. In the rear of our house is a lovely little tree that arches gracefully over and down to the lawn. That tree is poison sumac.
Chances are you will never need to know what poison sumac looks like, because poison sumac is a relatively rare plant that grows only in wetland. It’s cousin, poison ivy, however, is another story. If you have the strange feeling that there is more poison ivy now than there was in your youth, you aren’t imagining things. As we change the environment around us by expanding our suburban sprawl, many plants have gone extinct locally, finding the new setting to be unsuitable to their growing needs. But some plants find the new conditions to be ideal. We have created the perfect habitat for poison ivy at the edge of every parking lot, road, and suburban yard in New England.
The dangerous feature of poison sumac and poison ivy is an oil called urushiol. This oil gets onto the skin when the plant is touched. Urushiol can also be transferred from the plant to another surface, such as pet fur or gardening implements, and from there to skin. Or, far more dangerously, the oil can be released in the air through burning, and then inhaled.
Once exposed, urushiol oil soaks into the skin within minutes, and between 12 and 72 hours later, causes itchy blisters to form. The rash may appear to spread, but what actually happens is that the most exposed areas of skin develop the rash first. The rash may be miserable, but it isn’t contagious.
Many people assert that they are immune to poison ivy, but according to the American Academy of Dermatology, 85 percent of the population will develop an allergy to urushiol when adequately exposed. To put it another way, just because you didn’t get a rash the first few times you walked through poison ivy doesn’t mean that you are immune. Native Americans are often among the 15 percent of those who are resistant to urushiol, as centuries of selective pressure have given them an advantage against poison ivy and its kin.
Urushiol is also present in smaller quantities in mangoes, cashews, and pistachios, which are in the same family of plants. A small percentage of the urushiol-sensitive population may develop a rash from eating these foods. Ginkgo biloba is entirely unrelated to these plants, but it, too, contains traces of urushiol.
Given the pervasiveness of poison ivy, it behooves anyone with children or who spend time outdoors to learn how to recognize poison ivy. For this, a simple Google image search is an adequate starting point. As you look at the images, keep a few things in mind:
Poison ivy leaves look entirely innocuous. The single distinguishing feature is that the leaves come in sets of three. The shape, size, and glossiness of the leaves can vary tremendously.
Poison ivy vines grow along the ground beneath leaf-litter until they find a suitable tree to climb, so the plant can appear to be a low-growing bushy plant. Once it has found a suitable tree to climb, a poison ivy vine can eventually develop a woody, hairy-looking trunk.
While there are poisons that can be used to kill poison ivy, those same poisons can also harm the trees the poison ivy clings to, as well as poison the environment for the other plants and animals in the area. To remove poison ivy without poison, hand-pulling can be safe if precautions are taken. To do so, cover as much of your exposed skin with clothing as possible, and arm yourself with heavy dishwashing gloves. Avoid coming into any contact with the plant except with your gloved hands. Grasp the stems close to the ground, and slowly pull up as much of the creeping vines as you can, and either leave them to wither in the woods where nobody will walk, or double-bag them and put them out for the trash. Throw away the gloves, too, using caution not to touch them on the outside, and wash the clothing in hot water.
The leaves of poison ivy are at their most dangerous in the early Spring, when the coating of urushiol on the leaves is fresh and new, and the leaves themselves are still small and difficult to spot. Hot summer days are also dangerous times to be around poison ivy, because the oil can be carried right through clothing by sweat. The safest time to remove the plants is on cool days late in the growing season.
In the wild recesses of my backyard woods is a poison ivy vine as big around as my arm. We call her the “mother vine”. She and the poison sumac provide food for the birds and a glorious show of color in the Fall. Knowing their dangers makes it possible for me to garden around them and leave them in place as a part of the ecosystem. I will continue to do battle with the mother vine’s children, but she is a welcome resident of my wild yard.