Sorbus sitchensis, also known as western mountain ash and Sitka mountain-ash, is a small shrub of northwestern North America. A multistemmed shrub, it is endemic to northwestern North America, from the Pacific coast of Alaska, to the mountains of Washington, Oregon and northern California and eastward to parts of Idaho and western Alberta and Montana. It is widespread in British Columbia. A multistemmed shrub, it is endemic to northwestern North America, from the Pacific coast of Alaska, to the mountains of Washington, Oregon and northern California and eastward to parts of Idaho and western Alberta and Montana. It is widespread in British Columbia.