Tsuga mertensiana is a type of conifer tree commonly found in North America. It is also known as mountain hemlock or Alaska hemlock. The term hemlock is used to refer to several species of the genus Tsuga, including Tsuga mertensiana, Tsuga canadensis, and Tsuga heterophylla. Other synonyms for Tsuga mertensiana include western hemlock, black hemlock, and California hemlock. It is an evergreen coniferous tree that grows up to 230 feet in height and has a narrow, conical shape. The tree has dark green foliage and small cones that contain seeds. Tsuga mertensiana is an important timber tree and is also used in landscaping and horticulture.