The moderate climate and ample precipitation of the region lead to rapid regrowth of vegetation on untended sites, which can hamper fieldwork in the area. Many forests that covered the area were partly cleared for agriculture, timber, or burials in the early 20th century. These cleared and burned land plots sustain rich stands of secondary forest, featuring gorse, huckleberry, nettles, poison oak, salal, and blackberry. Myriad species of fern, as well as rapid-growth deciduous trees like alder and vine maple are also frequent. Forests support stands of Douglas fir, western hemlock, western redcedar, Pacific dogwood, bigleaf maple, Oregon ash, red alder, cascara buckthorn, Pacific madrone, and Oregon white oak; within swamps and moist areas in creeks, the shrub Devil's club can be observed. Other trees that sometimes dominate forest areas include black cottonwood. Forest communities have many additional shrubs including Indian plum, western hazel, and snowberry. Ground layer plants include the herbaceous sword fern and stinging nettle.