Thursday, May 16, 2019

California's state plant: Poison Oak

Nate and I recently backpacked the Skyline-to-the-Sea trail, an easy, well-marked, thirty-two mile route, from Castle Rock State Park to Waddell Beach, in Northern California. On the trail we saw a lot of: (1) poison oak, Toxicodendron diversilobum, and (2) hikers and backpackers who were aware of its presence, but could not identify it. That's probably because poison oak is a highly versatile and varied plant that can take advantage of many micro-climates and looks very different in each of them. For this reason it is hard to identify if you are not familiar with it. 
As someone who is highly sensitive to the oil produced by poison oak  I develop an oozy, itchy rash in the mere presence of its aerosolized droplets   I am always on the lookout for it. My poison oak souvenir from Skyline-to-the-Sea was a pencil point-sized lesion on my forearm, but other hikers and backpackers had welts on their legs, arms, and faces and didn't know when or where they had been exposed. The rash can take several days to emerge after exposure.

In this post I'll identify poison oak and share several pictures from our trip so you know what to look for and how to avoid touching this plant the next time you are out on the trail. 
(All photos taken on the Skyline-to-the-Sea trail between Castle Rock State Park and Waddell beach April, 2019.)

Poison oak is a native woody plant that has a three-leafed or leafleted cluster at the end of each stem. The leaves are toothed, lobed, or scalloped at the edges. There is usually a red or black appearance to the stem where the leaves diverge. Poison oak is deciduous. In the fall its leaves turn bright red and fall off. 
The plant can appear as ground cover, a woody shrub, a vine, or a tree. Poison oak prefers full sun, but can grow in moist shady environments as well. Most hikers run into it because they are not looking for it in the shade or overhead. 
A vining example of poison oak, which is young, weeping, and not very sturdy. It has the traditional three leaves, which are bright green and shiny, with scalloped edges. You will often see large poison oak vines climbing tree trunks at the side of the road or the side of your trail.
A lush variety of poison oak living in the redwood understory where it is mostly shaded and wet. The leaves are larger and thinner here than one would see in the full sun varieties. Note the red dot-like appearance of the stem where the three leaves diverge. 
Another vining, tree-like example of poison oak. It blends in with other nearby tree branches and is very hardy. Note the moss growth. 
A low, sturdy, poison oak plant growing in tufts, almost like ground cover, from a crack in this boulder. The leaves are fairly small, thick, and glossy looking.
Poison oak thriving in full sun. Each individual woody stalk has several clusters of small, sturdy, reddish-tinged leaves.

Nate standing below a dense poison oak plant that looks like a small tree. Look at the density of those woody stems!
No poison oak here, but while searching for it, I stumbled upon this western rattlesnake, Crotalus oreganus.

I hope these pictures and descriptions will help you stay itch free!

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