Poison oak has a good side, too

by on July 12, 2012

Photo by Sierrian on Flickr

Photo by Sierrian on Flickr

Poison oak gets a bad rap, and with good reason. The plant produces an allergenic oil, urushiol, that causes painful rashes on unsuspecting hikers and gardeners. But there’s also a good side to this hearty woodland shrub that may be worth keeping in mind as you trek into poison oak territory.

The plant is a California native, and while it may not seem valuable to humans, poison oak has a solid place in California ecosystems. As one of the most prevalent woody shrubs, poison oak is versatile, growing as a single stem in grasslands, or as a six-foot bush. It can also climb up to 40 feet, often high into the treetops of California oaks and even coast redwoods.

Poison oak turns brilliant colors in the fall, as this one in Tilden Regional Park in the hills above Berkeley. Photo by Philip Bouchard.

And most of us probably don’t appreciate it in this way, but poison oak, a member of the cashew family, has its beauty, too. In spring, it puts forth green leaves and white flowers that turn into clusters of tiny white berries by summer. In the fall the leaves turn vibrant shades of red, orange and yellow. The plant goes through winter bare of leaves. As the saying goes: “Leaves of three, let it be.”

“It’s probably one of the best fall colors in the lowlands,” says Anthony Fisher, a naturalist at Tilden Regional Park.

Humans may have no use for it, but many California animal species do. Unaffected by the toxic oil, small animals like fox squirrels seek shelter in poison oak thickets and feed on its summer berries, says Fisher. Birds — notably the California towhee — have formed a symbiotic relationship with poison oak, building its nests among the plants and feeding on the white berries, then spreading the seeds through excrement.

When rivers flood during the winter, the western pond turtle takes to poison oak patches for shelter. Meanwhile, large herbivores, such as deer, feed on the leaves and stems of the plant, while domesticated goats also happily munch away unharmed.

So what would happen if poison oak went extinct — as many a hiker might dream? Surely a diminished ecosystem. That being said, since we humans are apparently not as hearty as the California towhee or the western pond turtle, it’s important to take care. If you’re out on the trail or in the garden, watch out for its shiny, waxy-looking leaves that grow in clusters of three and resemble oak leaves.

Then give a nod of respect to this much maligned plant.

See more articles in: Plants and Fungi

8 comments:

Liam O'Brien on July 19th, 2012 at 12:00 am

It’s also know to be the host plant for some of our native “microleps” (tiny moths). Because they aren’t as big and showy as butterflies, it’s a group of nature that is greatly overlooked.
When I learned this from Jerry Powell, it made me look at this plant in a who new way.
I’m currently painting it for an Oak Woodlands trail sign and that red is magnificent!

baynature on July 19th, 2012 at 12:00 am

Sounds great, Liam! Another vote for poison oaks. And micro-leps. Can’t forget the micro-leps!

Laure Latham on July 20th, 2012 at 12:00 am

It’s always amazed me how poison oak doesn’t seem to affect wild animals. Is it the same with dogs who, apparently, can rub off some poison oak oil on your clothes because they went out in a big bush? I believe the dogs remain unaffected but you had better take precautions. Regardless, thanks for this article as I believe that everything has a purpose in nature, apart from mosquitoes whose purpose I will never understand. And yes, poison oak is one of the most vibrant fall colors in the Bay Area.

Marianne on June 30th, 2014 at 10:28 am

How about, it’s an aspect of nature that wants to remain untouched by human hands? If such provides shelter for animals and a food source for wildlife … Then serves a purpose without the manipulations of man …

Marianne on June 30th, 2014 at 10:31 am

Alittle bit more research … the medical site says Poison Ivy (which is the same chemical component as Poison Oak) … is utilized to treat pain …

Andy on August 28th, 2014 at 5:23 pm

I currently have poison oak everywhere.
This plant can go to hell from where it came.

Evan on October 2nd, 2014 at 8:41 am

Im with Andy……Im covered and in misery…..Eradicate this plant from the earth!!!!

TJ on April 5th, 2015 at 4:50 pm

I have a love/hate relationship with it. I typically hike and backpack at elevations where it doesn’t grow but on those occasions when I’m below 5K I love the attention it demands when I’m around it. Sort of an obstacle course. And when the leaves turn red it really is beautiful, especially in CA where we don’t get the same kind of colors as the East.

There’s also a lot of myths like you can become immune by eating small amounts of it, scratching will spread it and you can spread it to another person.

The REAL crazy poisonous plant? The Poodle Dog Bush. It only grows in burn areas, lasts for about seven years as it serves as protector for new growth, and then dies and goes dormant until the next fire. And the rash is way more insidious than poison oak. The drag is that it has a beautiful flower in the spring and early summer. I’ve pulled my car over many times to tell people that it probably isn’t the best idea to stand in the middle of a poodle dog bush. They’ll pay dearly for that mistake.

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