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, lawn, and patio shelter 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.
Ash trees are prone to borers. In some parts of California, ash whitefly is a problem; these chalky white, 1/8-in.-long insects colonize in patches on leaf undersides. Outbreaks are usually controlled by natural enemies; avoid spraying with broad-spectrum insecticides, which are likely to wipe out these beneficial predators.Fraxinus velutina
Native to the southwestern U.S. and Mexico. This deciduous tree withstands hot, dry conditions and is cold hardy to about –10°F/–23°C. Grows to about 30 ft. (possibly to 50 ft.) tall. Pyramidal when young; spreading to 30–40 ft. wide when mature, with a more open form. Leaves are divided into three to five narrow to oval, 3-in.-long leaflets; they turn bright yellow in fall. Male and female flowers on separate trees.‘Berrinda’
Very tough, cold-hardy selection from New Mexico, with a strongly upright form to 35 ft. tall and about as wide.‘Bonita’
Good substitute for ‘Modesto’, especially in the Southwest. Broadly oval to 30–35 ft. tall and slightly wider. Bright yellow fall color lasts longer than that of ‘Modesto’.‘Modesto’
Originated in Modesto, California. Vigorous form growing to about 50 ft. tall, with a 30-ft. spread. Leaflets are medium green, glossier than those of the species; bright yellow fall color. Resistant to oak root fungus but subject to so many other diseases that most communities have removed it from their lists of recommended trees. Good replacements include ‘Bonita’, ‘Rio Grande’, F. angustifolia ‘Raywood’, and F. uhdei.‘Rio Grande’
Thrives in hot, dry climates and alkaline soils. Has larger, darker green, more succulent leaflets than ‘Modesto’; they turn golden yellow in late autumn. Foliage is resistant to windburn.
Native to the Mediterranean region. Once valued for its bold effect in garden fringes and near water a...
Gray-green rosettes of many leaves are joined by fine hairs for a cobweb-covered look. Larger rosettes...
Native to the eastern and southern United States. Can climb to 10–20 ft. tall but is shrubby if ...