How to Avoid Poison Oak in Yosemite

This poisonous plant is the bane of my existence. Every spring & summer since I was a boy, I get an itchy rash from touching it. Of course, I don’t mean to, but it’s so common in elevations below 4,000ft in California. It’s not always easy to avoid it. Anyhow, here are photos and info on how to avoid poison oak in Yosemite.

Three Leaves in Spring, closeup  - Poison oak in Yosemite
Poison oak plant, early in the season

For the most part, I love the park – because the vast majority of it is at or above 4000ft. That is what I refer to as the poison oak line. It’s nice to be able to hike anywhere along Tioga Road’s high country – without any concern of coming into contact with the plant.

Green and red "leaves of three, let it be"
New growth is often deep red

In fact, for a long time I didn’t think there was any poison oak in Yosemite. I’ll never forget the first time I came across it while hiking near the road.

Where to Find Poison Oak in Yosemite

As far as I can tell, there are essentially just 2 heavily trafficked areas where you will see this plant.

El Portal Road, Along The Merced River

The #1 location to watch out for is El Portal Road, coming into the park. Right when you pass the entrance gate, there’s some incredible scenery. However, be wary…leafy, green poison oak grows all over the place here.

I pulled over to photograph the large roadside boulders – I was shocked to find that the plants were everywhere. There is a median between the two one-way roads. Not only did I see it there, but also all along the sides of the road. That also means it grows all the way down to the nearby Merced River.

Green plants in afternoon sunlight
The plant can look quite different, depending on where it grows

From this location, your elevation steadily rises as you progress into the park. Thankfully, you’ll see less and less poison oak as you keep driving.

Also watch out at the Cascades (Lower), along El Portal Road as well. I climbed and hiked up this canyon in winter to photograph the falls. I had no idea that the bare branches brushing up against me were in fact poison oak.

Red Leaves Closeup in Spring - Poison oak in Yosemite
Poison Oak Closeup in Spring

Of course, it also pays to be wary of the Merced River at this location. Soon after the Cascades turnout, the plant begins to disappear from the landscape. By the time you reach the SR120 / Big Oak Flat junction, it’s basically non-existent.

However, should you turn left onto SR120, I have seen a few roadside patches here and there, so just watch out for it.

Hetch Hetchy Reservoir

There’s really no other way to say this – Hetch Hetchy is infested with poison oak. I noticed it growing pretty much everywhere along the road, as well as all around the Hetch Hetchy valley.

On the drive in, I noticed a trailhead sign for the Poopenaut Valley. It looked promising, but I had to turn back half way down the steep trail. I had dropped in elevation and crossed the poison oak line. It was simply unavoidable after that.

Yosemite Valley is Safe

You can rest easy knowing that I have never seen poison oak growing in Yosemite Valley proper. By this, I mean anything beyond Pohono Bridge, when coming in on 120 or Highway 140.

How To Identify Poison Oak

I hope the photos above will help you avoid this toxic plant. Just remember the old saying “leaves of three, let it be.” Poison oak grows in clusters of three leaves, sprouting vibrant green (or red) shoots in spring. The plant is quite versatile, and can grow in a variety of lower elevation environments.

I’ve seen it in dry, sunny locations where the leaves look smaller – the green color is muted, and the leaf texture is shriveled and leathery. By contrast, in shady creekside forests it can grow large and leafy. These locations tend to have plants that are a vibrant green color.

The first few cold days of Autumn shock the leaves, turning them red once again. Afterward, they drop – revealing bare branches that still contain urishol, the oily irritant. Remember, while the oils on winter branches are not as potent, they can still cause a rash.

When I get these rashes, they usually develop around 24 hours of exposure to my skin. I then suffer for up to 3 weeks, sometimes with horrible puss-filled blisters.


I don’t take any chances after I’ve hiked somewhere where this plant grows. I carefully remove and wash my clothes right away when home. A cool shower is certainly in order, scrubbing my skin with Dawn dish soap. This seems to be the most effective (cost and otherwise) way to cut through and remove the oils.

Itch cream can be used for relief, and some people swear by Oralivy drops for prevention each season. If you live in a place like California and you’ve never had an allergic reaction, you probably don’t have to worry.

However, I have read accounts of hikers who have never gotten the rash in their entire lives. For whatever reason, later in life, they can suddenly develop the allergy. I’ll believe this when I meet them in person!

Supposedly 85% of people are sensitive to this plant, but in my experience it seems more like only 50% (or maybe even just 40%!). How I wish I was one of them.

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– Nathan Allen

About Me

Photographer Nathan Allen

I’m Nathan Allen, photographer / creator of (Yosemite Photos) and international travel site I Dreamed Of This. In truth, I lived in San Francisco, New York, & Singapore…but nothing compares to life in the mountains. I share my experiences HERE.