Subalpine Zone: At 5000' to 7000' in elevation on the north slopes and throughout the North Cascades you find meadows, shrubfields and patches of stunted trees. Fragile plants such as heather, partridge foot and Sitka valerian flourish in high elevation meadows. The shrubfields include slide alder and false azalea. Numerous alpine and subalpine flowers like phlox, Indian paintbrush, elephant head, columbine, Davidson's penstemon and mountain lupine cover the slopes.

Mountain Hemlock Zone: The highest area of continuous forest on the west side, 4000' to 5000' or more in elevation depending on exposure, includes mountain hemlock, Alaska yellow cedar, pacific fir and subalpine fir. Shrubs found at these elevations include false azalea, mountain ash and slide alder. Understory plants include twisted stalk and queen's cup.

Silver Fir Zone: At mid-elevation, 2000' to 4000', the trees found are primarily the pacific silver fir, western hemlock, western redcedar and sometimes Douglas fir. Shrubs found here are huckleberry and false azalea. The forest floor is similar to the Western Hemlock Zone, with a thick understory including Oregon grape, salal and many ferns.

Western Hemlock Zone: Consists of lowland forests along the west side river valleys. Dominant trees are western hemlock, western redcedar and Douglas fir. Shrubs and ground cover include vine maple, red huckleberry bushes, thimbleberry, sword fern, trillium and foam flower. In undisturbed areas the ground, tree trunks and branches are covered with mosses, mushrooms and lichens. The cool moist maritime climate provides plenty of rainfall, maintaining this forest community.

Eastside Meadow & Subalpine Fir Zone: At 4000' to 6500' elevation you'll find subalpine fir, Engelmann spruce, subalpine larch and whitebark pine mixed with a variety of other trees. Shrubs at these elevations are cascade mountain ash, white rhododendron, Oregon boxwood and huckleberry. The understory is much more open in this drier community due to less precipitation than on western slopes. The mountains act as a barrier against wet air moving inland off the Pacific Ocean and Puget Sound casting a rainshadow across the eastern slopes.

Douglas Fir & Lodgepole Pine Zone: This mid-elevation, 2000' to 4000', eastside community is primarily Douglas fir and lodgepole pine mixed with Ponderosa pine, grand fir and western larch. The understory consists of Douglas maple, oceanspray, bitterbrush, pine grass, mountain boxwood and spirea.