Poison oak, or Toxicodendron diversilobum or Toxicodendron pubescens, is another relative of poison ivy and poison sumac. There are two species of poison oak: eastern and western. Both species are common across North America in a variety of habitats, making it a good plant to recognize at first glance.
Like poison ivy and poison sumac, poison oak contains the compound urushiol. This substance gives a nasty rash if it comes in contact with your skin — even if you just get it from touching your pet’s fur or your affected boots.
About 80% of people will have an allergic reaction to urushiol, but most people’s reactions get worse over time. In other words, you might not react at all the first time you’re exposed to urushiol. But after each encounter, your reaction will get more severe.
Urushiol is especially dangerous if burned, making wildfires or s’mores sticks especially hazardous.
Poison oak is an important nurse plant for other species after disturbances. It’s also edible for many animals. If you can safely leave this plant where it is, it’s therefore good for many ecosystems to leave it alone.
Learn more about identification, distribution, removal, and treatment of poison oak below.
How to Identify Poison Oak
Poison oak can be tricky to identify. The common name includes two distinct species, and Western poison oak can grow in several different forms. When Western poison oak gets full sun, it grows as a bushy shrub. If it grows the shade of other trees, it’s more likely to grow as a climbing vine.
The leaves are quite variable as well. They generally grow in clumps of three (or occasionally five or seven) and loosely resemble the leaves of an oak tree. They are toothed or lobed, though not as deeply as oak leaves.
Western poison oak is generally glossy, while eastern poison oak has slightly fuzzy leaves. The leaves are one to four inches long. The leaves are often bronze in the spring, green in the summer, and reddish to pinkish in the fall.
True oak leaves do not grow in odd-numbered groups. Additionally, poison oak has whitish berries rather than acorns.
The stems are generally hairy or thorny.
In short, poison oak is pretty tricky to describe thanks to its wide variety of growth patterns. Keep an eye out for groups of three leaves with a hairy stem and white berries. When in doubt, leave it alone.
Where Does Poison Oak Grow?
Poison oak is divided into two different species: eastern and western. Western poison oak is common along the west coast from Baja California to British Columbia. Eastern poison oak grows in the eastern U.S., roughly from Virginia to Texas.
This plant grows well in a variety of habitats – grasslands, forest, and scrub. It does well in shade, partial sun, or full sun at most moisture levels below 5,000 feet.
Yet again, looking at the distribution and habitat of this plant isn’t very helpful. If you’re in the southeast or western portions of North America, there’s a good chance this plant could grow where you are.
How Can I Remove Poison Oak?
Poison oak removal is a bit of a chore. Generally, it’s best to hire a professional to remove poison oak — you are likely to expose yourself to its toxins if you remove it yourself.
If the poison oak is out of the way and unlikely to cause problems, you can always chose to leave it alone. Many people would rather be safe than sorry, though, and remove the poison oak.
If you would rather remove the poison oak yourself, it’s best to use a combination of manual removal and chemical treatment. Poison oak is a tenacious plant, and you’ll often have to repeat the removal process at least a few times.
- Identify the target and plan your removal for a dry, windless day.
- Gear up. Don’t forget goggles, a mask, and long clothing or rubber gloves and boots to cover your whole body.
- Cut the plant at ground level using shears. If possible, dig up the roots as well. Bag up any foliage in black garbage bags.
- Treat the remaining base using a chemical herbicide. We don’t always recommend these chemicals, but manual removal is risky with poison oak. It’s best to stack the deck in your favor using chemical assistance.
- Remember not to burn poison oak or put it in the compost. Instead, put it in black plastic trash bags. Check with your municipality to see if they allow these bags in the local dump.
- Disinfect your clothing and tools. Rinse tools with rubbing alcohol, then oil the joints after they’ve dried. Wash your gloves before removing your clothing, then use the gloves to take off all of your clothing. Wash all of this immediately, then wash your gloves again. Take a shower afterward.
Remember that burning poison oak releases the toxins into the air, which can cause serious (or even dangerous) reactions in your lungs. Some people will even react to poison oak from being near it and breathing it in, so be sure to wear a mask during removal.
How Do I Treat a Rash from Poison Oak?
Luckily, poison oak isn’t quite as serious as poison sumac. That said, poison oak rashes in the lungs, face, or across a large portion of your body can be quite serious. Some people are far more allergic to poison oak than others, resulting in extra-nasty reactions.
As soon as you realize that you might have touched poison oak, rinse the affected area with lots of cool water and degreasing soap (like dish soap). This may help reduce the spread of the oil (which contains urushiol).
There is no way to stop a poison oak reaction. You’re likely going to deal with a rash for at least three or four weeks. However, you can reduce the effects of your reaction by using topical creams and oral antihistamines. Benadryl, oatmeal baths, calamine lotion, and hydrocortisone creams are all decent options.
Try your best not to scratch the rashes from poison oak. This can lead to infection, prolonging your misery and ending in scarring.