Poisonous plants

County Agent’s Corner



Q: Since I have been spending a lot of time at home, I have crossed several items off my garden “to do” list. However, there is one item that I have not managed to tackle just yet – cleaning up a natural area behind my house. I want to make sure I steer clear of any poisonous plants, but I am not quite sure what all I may encounter. Can you help?

A: You are one of many who has been spending a lot of time in their gardens and landscapes. I am happy to share some plant information with you. Just know that you may also run across some wildlife that you want to avoid, as well, but that is a topic for another article.

As you start cleaning up your natural area, you most likely will encounter one or more of the most common poisonous plants in Alabama – poison ivy, poison oak, and poison sumac.

It can be a challenge to distinguish whether you have poison ivy or poison oak. Each has leaves with three leaflets that join together at a red center. These two species are responsible for the old adage “leaves of three, let them be.” The leaflets are commonly two to eight inches long and 3/4 to five inches wide and have scattered, jagged teeth along the edges. One visual difference relates to the shape of the leaflet edges. The edges of the teeth on the leaflets of poison oak are rounded, and those of poison ivy are pointed.

Another difference is the growth habit of each plant. Poison ivy grows as a vine that may run along the ground or up the sides of trees, houses, or other vertical surfaces. The vines, which can vary in size from less than 1/4 inch to more than two inches in diameter, appear “hairy” due to tiny roots that extend from the vine. In contrast, poison oak is shrub like in appearance and has stems up to three feet tall.

Poison ivy is found in a wide variety of habitats and is especially common in wooded areas and along forest edges. Poison oak is typically found in drier, more open forests, fields, and rights-of-way.

Poison sumac is a close relative of poison ivy and poison oak, but it looks very different. The leaves of poison sumac have seven to 15 leaflets that are commonly two to four inches long and 3/4 to two inches wide. The leaflets, which are arranged along the stem in pairs, are oblong with sharply pointed tips and smooth edges. The stems and leaf stalks are often a bright red color. Poison sumac grows as a shrub or small tree, reaching up to 20 feet tall in open or wooded swampy areas.

Touching any of the three poisonous species may result in an itchy rash of blisters. One out of every two people is allergic to toxicodendrol, an oily compound found in all parts of these plants. Simply touching the leaves may expose you to the oil, and additional oil is released when plant parts are crushed or damaged. The oil resists breakdown and may cling to clothing, tools, and pet fur for long periods of time and may even persist on a secondary surface for up to a year. Touching these secondary surfaces can also cause an allergic reaction. Although not everyone is allergic to these plants, allergies may develop with increased contact; therefore, even people who do not seem allergic now should avoid these plants.

In your case, it sounds like avoidance may not be an option. There is an extremely high probability that you will encounter poison ivy as you clean up your natural area. However, following these tips will be extremely helpful in limiting your exposure:

• Always wear long pants and close-toed shoes when in wooded areas or fields.

• Carefully inspect tree trunks before touching them since poison ivy often clings to them.

• Always wash clothes immediately upon return from outdoor recreation.

• Be wary of leafy, green plants that carpet the forest floor. Poison ivy and poison oak commonly grow in this fashion.

• Wash skin with cold water and soap or rubbing alcohol within 10 minutes if contact is suspected. Do not use hot water as this may make the problem worse by opening skin pores.

• Do not eat any part of these plants.

• Do not burn any part of these plants. The allergen can become airborne and be inhaled.

• Consider hiking in late fall or winter when these plants have dropped their leaves.

• Wear vinyl gloves with long sleeves tucked in when weeding gardens.

• Apply a preventative lotion (several brands available) before going outdoors.

Good luck and happy gardening!

This column includes research-based information from land-grant universities around the country, including Alabama A&M and Auburn Universities. Email questions to O’Rear at Bethany@aces.edu or call 205-612-9524. Like us on Facebook. Follow us on Twitter. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University), is an equal opportunity educator and employer.