These mountain natives are valued for their showy flowers and even showier fruit. Blossoms are grouped in broad, flat clusters that are scattered over the foliage canopy in spring; they develop into hanging clusters of small, berrylike fruit that colors up in late summer or early fall. Most species have red or orange-red fruit, but white, pink, and golden forms are occasionally available. Birds feed on the fruit, but usually not until after leaves have fallen. Foliage is typically finely cut and somewhat fernlike, though some less widely planted species have undivided leaves.
Mountain ashes need some winter chill, and their dislike of extended summer heat makes them poor choices for most of the South. Where adapted, they are good small garden trees or street trees, though fruit can make a mess on paved surfaces. Provide good, well-drained soil. Like other members of the rose family, they are subject to fireblight. Borers and cankers are problems for plants under stress.
S. alnifolia. KOREAN MOUNTAIN ASH. Tree. Zones US, MS, LS; USDA 6-8. From China, Korea, Japan. Dense growth to 4050 ft. tall, 2030 ft. wide. The specific name alnifolia refers to the leaves, which are undivided (like those of alder, Alnus); they are 24 in. long, toothed, dark green, turning yellow to orange in fall. Reddish pink to orange-red fruit. Grayish bark is mottled with white. Tolerates heat, drought, and humidity better than other mountain ashes. Takes acid or alkaline soils and is less susceptible than its kin to borers.
S. americana. AMERICAN MOUNTAIN ASH. Tree or shrub. Zone US; USDA 6. From eastern North America. Grows 1030 ft. tall and wide. Dark green leaves with paler undersides are 10 in. long and consist of 11 to 17 leaflets; turn yellow in fall. Orange-red fruit. This species is very hardy and tolerates damp soil, but it is not the choicest of mountain ashes. Attractive in its native mountainous environment. 'Red Cascade' grows just 18 ft. tall and 8 ft. wide, with an attractive oval crown.
S. aucuparia. EUROPEAN MOUNTAIN ASH. Tree. Zones US, MS; USDA 6-7. Native from Europe to western Asia and Siberia; naturalized in North America. To 2040 ft. tall (or taller), 1525 ft. wide. Sharply rising branches form a dense, oval to round crown. Leaves are 59 in. long, with 9 to 15 leaflets; they are dull green above, gray-green below, turning tawny yellow to reddish in autumn. Orange-red fruit. 'Cardinal Royal' has especially large bright red berries. 'Black Hawk' and 'Fastigiata' are slightly narrower, upright forms.