In the understory of a temperate rainforest, smaller trees and shrubs grow in the abundant moisture and shade among the trunks of the tall trees. Nearly every bit of space is taken up by living plants. The thick understory of skunk cabbage and devil's club make passage difficult. Some plants adapt to the wet soil by developing shallow root systems. Others have air pockets that allow oxygen to travel from leaves to roots. Many different mosses, lichens and ferns also thrive here, absorbing water and nutrients from rain and fog.

Devil’s club (Oplopanax horridus) is named for the long spines covering its woody stems, which can be 3-9 feet (1-3 m) tall. Each thorny stem supports large maple-shaped leaves, also with thorns, and topped with a pyramidal stalk of numerous small, greenish-white flowers in spring that turn into red berries. Devil's club can be found in large thickets in wet areas, like this one along the Old Mine Tail. This thorn-covered shrub can make off-trail travel challenging to say the least, but it also has many medicinal properties highly valued by native people.