"Erysiphe berberidis" is a fungus that causes powdery mildew on Oregon grape leaves. The understory is primarily composed of salal, hazel, salmonberry, devil's club and Oregon grape. Understory plants include Idaho fescue, bluebunch wheatgrass, antelope bitterbrush, Oregon grape, hazel, and snowberry. Vine maples, rhododendron, Oregon grape, huckleberry, and thimbleberry grow beneath the trees. Shrubs such as Oregon grape, honeysuckle, blue elderberry, and Pacific poison oak also grow here. Some Indigenous peoples of the Northwest Plateau use Oregon grape for dyspepsia. The ground cover includes snowberry, Oregon grape, salal, sword fern, trillium, and fawn lily. The chaparral features Oregon grape, western fescue, snowberry, bluebunch wheatgrass, and ceanothus. Cascade, low, dull, or dwarf Oregon grape ("M. nervosa"); and creeping Oregon grape ("M. repens").