Showy mountain ash (Sorbus decora) also known as northern mountain ash is a native of Iowa. It is a large shrub or small tree similar to the American mountain ash, but different because the leaflets are narrow, oblong-oval, only 2 to 3 times as long as broad with a pointed tip, and paler (whiter) beneath.
Habitat: Found only in extreme northeast Iowa, requires well drained fertile soil.
Hardiness: Zones 3 through 9
Growth Rate: Moderate to Fast
Mature Shape: Slightly pyramidal, upright with a rounded crown
Height: 50- 80 feet
Width: 50-70 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.
Leaves: Opposite-branching and pinnately compound
Flowering Dates: May - July
Seed Dispersal Dates: August - June
Seed Bearing Frequency: Yearly
Seed Stratification: Prechill for 2 months at 34°F to 40°F
The flowers are larger than American mountain ash; 3/8 inch across, and the cluster is more diffuse. The fruits are also larger at 3/8 inch across.
Its range is from southern Greenland, Labrador, and Newfoundland westward to northern Ontario and Minnesota; and southward to Maine, New York, Ohio, northern Indiana, and extreme northeast Iowa. It can be found naturally occurring in woodlands and on rocky shores and slopes preferring well drained rich soil.