The Concolor Fir tree, Abies concolor, is also known as white fir, concolor fir, silver fir, Rocky Mountain white fir, Colorado Fir, Lows Fir, Pacific white fir. Concolor Fir trees are large, densely-growing, narrow trees with a dome-shaped crown growing to 50 feet or more. This evergreen conifer tree is native to the mountainous regions of the western United States. This rapid growing fir tree is the most drought-resistant of all native firs. Although it can exist on poor, dry sites, the white fir grows most vigorously in moist, well-drained, acid soils in protected locations. It is a rapid grower after it becomes established. It makes a handsome ornamental and decorative Christmas tree.