Cascade Mountain Ash, Cascade Mountain-ash, Greene's Mountain Ash, Rocky Mt. Mountain Ash: Sorbus scopulina (Synonyms: Pyrus scopulina, Sorbus cascadensis, Sorbus scopulina var. cascadensis, Sorbus scopulina var. scopulina) - Small tree to 12 feet. Flowers small, white, in round clusters like an overturned plate (cyme). Leaves compound pinnate, very shiny, with small serrations along the full length of the leaflet margins. Leaflets number 9-13 with acute to acuminate tips.
Dwarf Mountain Ash, Gray's Mountain Ash, Sitka Mountain Ash, Sitka Mountain-ash: Sorbus sitchensis var. grayi (Synonyms: Pyrus occidentalis, Sorbus occidentalis, Sorbus sitchensis ssp. grayi) - Small tree to 12 feet. Flowers small, white, in round clusters like an overturned plate (cyme). Leaves compound pinnate, a dull blue-green, with small serrations along the distal 1/2-2/3 of the margins of the leaflets. Leaflets number 7-11 with blunt to rounded tips.