American Mountain Ash

The American mountain ash (Sorbus americana), also known as mountain ash or roundwood, is a deciduous small to medium size tree, attaining a height of 30 feet (maximum 71 feet), and a trunk diameter of more than 1 foot. It does not grow rapidly and is considered a short-lived species.

The leaves are alternate, pinnately compound, 6 to 10 inches long with lance-shaped leaflets that are 2 to 3 inches long; fine and sharp toothed margins, dark yellow-green on top and paler beneath.

light gray-brown American mountain ash bark — American Mountain Ash Bark, Photo by Keith Kanoti, Maine Forest Service, Bugwood.org

The fruits are pomes (berry-like), 1/4 inch in diameter, in large clusters, and an orange-red color when mature.

Hardiness: Zones 3 through 9

Growth Rate: Moderate to Fast

Mature Shape: Slightly pyramidal, upright with a rounded crown

Height: 50 to 80 feet

Width: 50 to 70 feet

Site Requirements: Native to Iowa, ash trees grow best in full sun and moist, well-drained soils. Ash trees are tolerant of a wide range of soil conditions.

Flowering Dates: May - July

Seed Dispersal Dates: August - March

Seed Bearing Age: 15 Years

Seed Bearing Frequency: Yearly

Seed Stratification: Seeds need cold stratification for 2 months at 34°F to 40°F

The twigs are thick, smooth, and gray to red color. The bark is light gray-brown, smooth on younger trunks, and rougher on older ones.

Considered a beautiful ornamental tree with no commercial value, it is commonly found in disturbed forest edges, cold swamp and bog margins, and rocky outcrops. Distinctly a northern species, it ranges from Newfoundland to Manitoba south to the northern portions of the United States and along the Appalachian Mountains to North Carolina.