Japanese Rowan Sorbus commixta

Sorbus commixta, or Japanese Mountain Ash, is a small to medium-sized deciduous tree that can reach a height of 23 to 33 feet. It has a rounded crown and brownish to silvery-grey bark. The leaves change to a deep purple or red in the fall, the white flowers are very attractive in the summer, and the bright orange fruit in the fall is a food source for birds. The plant can tolerates strong winds but not maritime exposure.

The JapaneseMountain Ash grows best in moist, acidic, well-drained soils in full sun. It is widely planted in northern North America as an ornamental and has naturalized in some parts of Canada and the northern U.S. Mountain ashes have ash-like leaves, but are members of the rose family, and are not related to true ashes (Fraxinus), which are in the olive family.

Insects, Diseases, and Other Plant Problems

Bacterial fireblight can be a severe problem, causing scorched leaves at the branch ends. Scab can cause significant defoliation. Cankers, crown gall, powdery mildew and rust may also occur. Insect visitors include aphids, sawfly, scale and borers. Stressed trees are particularly vulnerable to borers and cankers.