Poisonous Plants

Identify, prevent and treat
By Barbara Mulhern

You’re a landscape maintenance worker who often works in wooded areas or among weeds or tall brush. You generally wear a long-sleeved shirt, long pants, socks, sturdy boots or shoes and gloves, but on this particular day it’s extremely hot, so you wear a short-sleeved shirt to work and leave the gloves in your truck.

A day or two later, an itchy rash breaks out on part of your arm. A similar rash that starts as small, red bumps subsequently appears on your hand. You try to ignore it, but after awhile blisters develop and the rashes begin to ooze.

It’s very likely that you came into contact with a poisonous plant. Exposure to the oil found in plants such as poison ivy, poison oak and poison sumac can not only be annoying, but in some cases, may be much more serious. Exposure to wild parsnip can result in large blisters that leave scars lasting as long as two years.

“Knowing what these plants look like—identification—is key,” says Thao Le, marketing director for Hyland’s (, a company that develops and markets homeopathic products, including a product that helps prevent poison ivy, oak and sumac rashes before they start. Prevention, she adds, is also critical. “Most people believe that wearing protective clothing is sufficient, but that is not true. The oils can stay on your tools or clothes. Wearing protective clothing is not enough.”

How do you identify a poisonous plant? Numerous resources are available, including the cooperative extension service in your area, various Web sites and your state department of natural resources. One good resource is, a first aid and consumer health information Web site written by physicians. This Web site describes poison ivy, poison oak and poison sumac as follows:

Photo by Piotr Jedrzejuk, www.Piotrpix.Com. Photo by Robert H. Mohlenbrock, Usda-Nrcs.
Poison ivy leaves. Poison sumac leaves.

The appearance of these plants varies from region to region and with the seasons.

In some parts of the country, including the Midwest and New England, landscape workers may also come into contact with wild parsnip, which is commonly found along roadsides, in poorly maintained prairies or bordering farmed fields. Wild parsnip grows to be 4 to 5 feet tall. When in bloom during the summer months, it has many large flat clusters of yellow flowers on a single, thick stem.

Here is some additional information about poisonous plants:

Prevention and treatment

Be on the lookout for poisonous plants in your area. Since it might be difficult to completely avoid them when mowing or performing other tasks, take the following steps:

Barbara Mulhern is a Belleville, Wis.-based agricultural/horticultural freelance writer.