Fairly fast-growing trees, most of which tolerate hot summers, cold winters, and many kinds of soil, including alkaline sorts. Chiefly used as street, shade, and lawn trees. In most cases, leaves are divided into leaflets. Male and female flowers (generally inconspicuous, in clusters) grow on separate trees in some species, on the same tree in others. In the latter case, flowers are often followed by clusters of single-seeded, winged fruit, often in such abundance that they can be a litter problem. When flowers are on separate trees, you'll get fruit on a female tree only if a male tree grows nearby.
Ashes are prone to borers, and in 2002, a particularly destructive type was found to have made its way to the U.S. from Asia. The emerald ash borer (EAB) is a -in.-long, dark metallic green beetle in the adult stage; the larvae, which can reach 1 in. long, feast beneath the tree's bark and cut off the supply of water and nutrients to the branches above. Most of an infected tree's canopy will die within 2 years. Adults can fly up to mile from tree to tree, and the pests are also believed to be spread by ash firewood being shipped from one area to another. EAB has been found in Georgia, Kentucky, Maryland, Missouri, North Carolina, Tennessee, Virginia, and West Virginia. There is no effective treatment so far. Contact your local Cooperative Exension Office for more information.
F. americana. WHITE ASH. Deciduous. Zones US, MS, LS, CS; USDA 6-9. From eastern U.S. Reaches 80 ft. or more, with straight trunk and oval-shaped crown to 50 ft. wide. Leaves 815 in. long, with five to nine oval, 2- to 6-in.-long leaflets; dark green above, paler beneath. Foliage turns purplish in fall. Male and female flowers on separate trees, but plants sold are generally seedlings, so you don't know what you're getting. If you end up with both male and female trees, you will get a heavy crop of seed; both litter and seedlings can be problems. Give this tree regular water.
Seedless selections include 'Autumn Applause' and 'Autumn Purple', both with exceptionally good, long-lasting purple fall color; 'Champaign County', a dense grower with pale yellow fall color; 'Greenspire', narrow, upright habit, deep orange fall color; 'Rosehill', with bronzy red fall color; 'Royal Purple', upright grower with purple autumn leaves; and 'Skyline', an upright oval with brown and purple fall color.
F. berlandierana. MEXICAN ASH. Deciduous. Zones MS, LS, CS, TS; USDA 7-11. From southern Texas and northeastern Mexico; often found along stream banks. Grows very fast when young, eventually reaching 3040 ft. tall, with a symmetrical, dense crown (to about 25 ft. across) that provides good shade. Glossy green leaves are made up of three to five leaflets to 4 in. long. Moderate water.
F. cuspidata. FRAGRANT ASH. Deciduous. Zones MS, LS, CS, TS; USDA 7-11. From Texas, Southwest, Mexico. Bushy shrub or small tree, 1015 ft. tall and broad, sometimes 20 ft. Leaves are divided into seven 212-in.-long leaflets; turn yellow in fall. Long panicles of white, vanilla-scented flowers cover the tree in mid- or late spring, making a very showy display against a dark background. Tolerant of drought and alkaline soil. Grows fast if watered regularly.
F. greggii. LITTLELEAF ASH, GREGG ASH. Evergreen. Zones MS, LS, CS, TS; USDA 7-11. Native from Arizona to Texas. To 25 ft. tall and 20 ft. wide, with leaves divided into three to seven 34-in., leathery, bright green leaflets. Useful desert tree. Little water.
F. ornus. FLOWERING ASH, MANNA ASH. Deciduous. Zones US, MS; USDA 6-7; best in Upper South. From southern Europe and Asia Minor. To 3040 ft., with rounded crown 2030 ft. wide. Luxuriant foliage mass: 8- to 10-in.-long leaves divided into 7 to 11 oval, medium green, 2-in.-long leaflets with toothed edges. Foliage turns to soft shades of lavender and yellow in fall. In spring, displays quantities of fluffy, branched, 3- to 5-in.-long clusters of showy, fragrant, white to greenish white blossoms. Moderate water.
F. pennsylvanica. GREEN ASH. Deciduous. Zones US, MS, LS, CS; USDA 6-9. Native to eastern U.S. To 5060 ft. tall, with irregular oval crown 2530 ft. across. Gray-brown bark; dense, twiggy structure. Bright green leaves 1012 in. long, divided into five to nine rather narrow, 4- to 6-in.-long leaflets. Inconsistent yellow fall color. For assured fall color, plant a named selection. Male and female flowers on separate trees. Takes wet soil and severe cold, but foliage burns in hot, dry winds. Regular water.
Seedless kinds include 'Emerald', a round-headed tree with glossy, deep green leaves and yellow fall color; 'Georgia Gem', with large, bright green leaves and good heat tolerance; 'Marshall's Seedless', a male form with lustrous, deep green foliage and good yellow fall color; 'Summit', upright habit, good golden yellow fall color; and 'Urbanite', pyramidal shape and bronze fall color.
F. texensis. TEXAS ASH. Deciduous. Zones MS, LS, CS; USDA 7-9. From Oklahoma and Texas. Round-headed tree to 3550 ft. tall and wide, fairly fast growing. Leaves have five dark green, 3-in.-long leaflets, which may turn shades of gold, orange, maroon in fall. Particularly suited to rocky limestone soils, but well adapted to regular garden watering and average soil. Usually long lived. Very drought tolerant.
F. velutina. ARIZONA ASH. Deciduous. Zones US, MS, LS, CS; USDA 6-9. Southeastern native. Takes hot, dry conditions and cold to about 10F. To 30 ft. (possibly 50 ft.) tall. Pyramidal when young; spreading 3040 ft. wide when mature, with a more open shape. Gray-green leaves are divided into three to five narrow to oval, 3-in.-long leaflets; turn bright yellow in fall. Male and female flowers on separate trees. Regular water.
'Rio Grande' ('Fan-Tex') is most commonly grown in Texas. Its leaflets are larger and darker green than those of the species; they resist wind burn.