While there are no “bad” plants, there are plants that grow where we would prefer they didn’t. Here at the Gardzen Test Garden in coastal North Carolina, USA, we recently found an unwanted visitor in the form of poison ivy (Toxicodendron radicans) growing along the side of a building. You’re probably familiar with this plant; it’s a rather pretty vine with lush green foliage that causes horrible itchy rashes in many people. We’re currently taking a break from poison ivy removal to write a blog about poison ivy and related plants. Learning how to identify poison ivy, poison oak, and poison sumac is important for any of us who spend time outdoor or around plants. Spotting them is the first step to avoiding them and sparing ourselves weeks of discomfort. So let’s dig in and learn about these plants, how to avoid them, and how to remove them if they find their way to your garden.
Identifying and Avoiding Poison Ivy and Similar Plants
Let’s start with the important part and learn how to identify these plants. We’re including a really great photo from the Cleveland Clinic, which also has some great information about treating poison ivy rashes should they occur. It’s important to understand what we’re looking at, so let’s talk about these plants one by one.
Poison ivy (Toxicodendron radicans and Toxicodendron rydbergii) is probably the most common and certainly the most well known of these plants. Poison ivy is found across North America, and while it’s technically two species we’ll treat it as one as they look so similar. Poison ivy is a bushy vine with clusters of three leaves each. The foliage is a dark lush green when mature but turns red, yellow, or orange in the autumn. The old adage “Leaves of three, let it be” is a good way to remember that bushy vines with three leaf clusters are best avoided. Poison ivy can spread by seed—birds love to eat the berries—or by root and stem sections in the soil.
Poison oak (Toxicodendron diversilobum and Toxicodendron pubescens) is like poison ivy technically two species but we’ll treat them as one due to their similarities. Found throughout the US and Canada, poison oak is a shrub up to 3 feet/one meter tall. Like poison ivy, its oak-like leaves grow in clusters of three leaflets—“leaves of three, let it be”. The roots are rhizomes, which not only means that this plant spread by via both roots and seeds but also that it tends to grow in clusters.
Poison sumac (Toxicodendron vernix) is another shrub or small tree. Found in the eastern United States and eastern Canada, poison sumac can grow up to 25 feet/8 meters in height. Its leaves look like “true” sumac leaves, with dark green alternate clusters of 7 to 15 leaflets each. The flowers are a pretty green-yellow, and the fruit they produce is much loved by birds, rabbits, and squirrels. Overall poison sumac is an attractive plant, but it’s best avoided as contact with it causes the same rashes and sores as poison ivy and poison oak.
Symptoms and First Aid for Poison Ivy, Poison Oak, and Poison Sumac
All three of these plants contain the same compound, an oily substance called urushiol. Many humans experience a strong reaction to contact with urushiol, including a red, itchy rash, blisters, and redness or swelling. Some folks are more sensitive than others, so not everyone has the same degree of urushiol reaction.
It is frighteningly easy to come into contact with urushiol. Direct contact with poison ivy, poison oak, or poison sumac is the most common way. However urushiol lingers on surfaces so you may come into contact with it on a surface that has brushed up against one of these plants. Outdoor pets can come into contact with an urushiol-bearing plant and then transmit that to their humans. Ingesting any part of the plant can lead to a reaction—this includes inhaling or coming into skin contact with smoke from burning plants!
If you suspect contact with poison ivy, poison oak, or poison sumac, the first thing to do is clean the affected area thoroughly with soap and water. Rashes are can last for a few weeks and recovery is uncomfortable so we really recommend vigilance in avoiding them. If a rash develops, cool water baths and lotions can help—talk to your pharmacist for recommendations. You should see a doctor if any of the following occurs:
· The reaction is severe or widespread
· Your skin continues to swell
· The rash affects your eyes, mouth or genitals
· Blisters are oozing pus
· You develop a fever greater than 100 F (37.8 C)
· The rash doesn't get better within a few weeks
Generally speaking, urushiol reactions are just uncomfortable and annoying. However some cases do require medical attention so please keep an eye on your symptoms and consult a doctor if needed.
Poison ivy, poison oak, and poison sumac are interesting plants in their own right, and can be quite pretty. They’re best appreciated from a distance, however, and they probably don’t belong in most gardens. We hope this blog helps you understand them a bit better and that you now know how to avoid them and the problems they cause.
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