The Cascades are a secondary mountain range between the Coast Mountains and the Rocky Mountains, stretching across the States of Washington and Oregon to join the Sierra Nevada in California. The woodlands there are mostly of the Douglas-fir-western-hemlock forest type. Douglas fir is now well established in Europe for its rapid, upright growth and excellent wood quality — the wood material is also sold as ‘Oregon’. On the other hand, Hemlock, less appreciated due to its lower wood quality, feels more at home in Tervuren, as evidenced by vigorous natural rejuvenation that can be seen everywhere in this part of the arboretum. The group was originally laid out on the slope according to the altitude zones in the mountains of origin. At the bottom, among others, were tree species from the valleys, including the Big-leaf maple and the now disappeared Balsam poplars. Ascending the slope, one also finds Western red cedar and Grand firs scattered throughout. In the middle of subgroup 3A, the lower part, stands the height champion of the arboretum: A tall Grand fir that soars above 50m. At a real mountain altitude, the Mountain hemlock and the Pacific silver fir are next to Engelmann spruce and Lodgepole pines that are at the end of their lives here. Graceful Noble firs tower behind these trees.