 Most of the High Cascades are therefore white with snow and ice year-round.The western slopes are densely covered with Douglas-fir ("Pseudotsuga menziesii"), western hemlock ("Tsuga heterophylla") and red alder ("Alnus rubra"), while the drier eastern slopes feature mostly ponderosa pine ("Pinus ponderosa"), with some western larch ("Larix occidentalis"), mountain hemlock ("Tsuga mertensiana") and subalpine fir ("Abies lasiocarpa") and subalpine larch ("Larix lyallii") at higher elevations.Annual rainfall is as low as on the eastern foothills due to a rain shadow effect.