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Poison Oak in October

“Leaves of three, let them be,” says an old cautionary tale. This is because plants like Poison Oak and Poison Ivy grow in clusters of three leaves, two on opposite sides of the stem and a third at top. Poison oak leaves are shaped in lobes, resembling the leaves of an oak tree.

As a common shrub in California at altitudes under 5000 feet altitude, poison oak must be watched for everywhere. Merely brushing your skin against the plant is enough to cause a rash of red pimples and even blisters. Blistering can last from 3 to 10 weeks.

When poison oak leaves are damaged by contact, it exudes urushiol oil which, upon contact with the skin, penetrates to the dermis to cause allergic reaction. The oil can easily be transferred from clothing, pets or inanimate objects to skin at a later time, and can stay active from 1 to 5 years. The amount of oil on the head of a pin would be enough to make 500 people itch.

On the west coast, poison oak can be seen growing on long vines, or along fences, often forming a

Poison Oak in March

dense mass of vegetation. Leaves are about six inches long and bright green in the spring. They turn yellow-green in the summer, and then bright red and dark brown in autumn before falling away in winter. Poison oak produces berries with a greenish-white color as well as yellow-green flowers.

Like poison oak, poison ivy contains urushiol which can cause a highly itchy rash, with allergic reactions lasting from 5 days to two weeks. Every part of the plant remains active even after the plant has died, making even dead leaves dangerous. If you can’t avoid areas where poisonous plants grow, be sure to wear closed shoes, long pants and long sleeves when hiking.

Knowing how to detect plants like poison oak and poison ivy will go a long way to protecting you on hikes in the wilderness.

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