New York Times story.
"COLUMBIA, Calif., Sept. 22 - It is peak season for fall foliage, when the foothills of the Sierra Nevada ... turn spectacular shades of crimson and russet.
...
Let leaf-peepers in New England ooh and aah over maples and mulled cider: here, fearless citizens like Bob Beck, a 69-year-old floral designer, risk dermatological disaster to harvest comely sprays of Toxicodendron diversilobum for what may be the country's strangest autumn ritual: the Annual Poison Oak Show.
"It's like a Visa card," Steve Bechtold, a park interpreter, said of the pervasive species that turns the California landscape, as well as human skin, a vivid red. "It's everywhere you want to be."
..."