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As a poison oak sufferer, I always assumed everyone knew how to identify a patch of the plant, but recently heard a fellow hiker admit they didn’t know what it looked like! So I did some research. Poison oak, or toxicodendron diversilobum, is the West Coast cousin of poison ivy. The leaves of both plants are covered by an oil called urushiol, which causes a red, bumpy, itchy rash that takes at least ten days to recede. Though a lucky few are immune, contact with poison oak can result in a range of reactions, from mild itching to severe, life-threatening systemic inflammation. Urushiol is nothing to mess with – the chemical is so tenacious that it has been found on Native American artifacts, still potent 1,000 years later.
Here is what you need to know in order to avoid an uncomfortable couple of weeks: Depending on its size, poison oak can look like a woody vine, a thicket, or a shrub. The leaves themselves are usually in groups of three and can vary from large, flat, matte, and green, to small, sharp, shiny and reddish. All hikers in the west would do well to remember the mantra,“Leaves of three, let it be.” “If it’s hairy, it’s a berry” is another helpful rhyme – the stems of berry plants have small thorns or hairs on their stems, while poison oak has a smooth stem. Be careful, though! Poison oak often grows in and amongst berry bushes, so often it’s better to steer clear of both. Oh, and don’t think you’re home free if the stalk doesn’t have any leaves….just the stems of poison oak plants can harbor urushiol as well.
Is there any upside to poison oak? Turns out that, while it may be a pest to humans, it makes great forage and habitat. Poison oak is rich in phosphorous, sulfur, and calcium, so the leaves and berries are a valuable food source for deer, birds, and other wildlife. It provides shelter for birds and small mammals, has been found to contribute to overall bird density and diversity in California, and provides great erosion control. Also, the plant is thriving in these warming times. High temperatures and CO2-rich air have caused woody vines like poison ivy and oak to grow at 150% their normal rate, according to a Duke University study.
So now you know what it looks like, but what should you do it you come in contact with some? If you touch poison oak or think you have been exposed to it, the first thing to do is wash the area thoroughly with soap. If you have access to them, specialized products like Technu and Zanfel are great for removing urushiol and keeping the rash at bay. Next, wash your clothes in hot water, separately from unaffected laundry. If you took your dog on the hike, consider taking your furry friend in the shower with you: urushiol can stay on their fur, so your pet can inadvertently spread the oil all. Lastly, if over-the-counter remedies are not making any impact on your ensuing rash, contact your doctor and they’ll get you fixed up.
Learn more about poison oak here.
May all your hikes be poison-oak-free this summer!
Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 76,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties.