Once highly prized shade trees, elms have fallen on hard times. Dutch elm disease (spread by a bark beetle) has killed millions of American elms throughout North America and can attack most other elm species. Many of the larger elms are appealing fare for various beetles, leafhoppers, aphids, and scale, making them time consuming to care for, messy, or both. Elms have other problems not related to pests. They have aggressive, shallow root systems, so you'll have trouble growing other plants beneath them. Many types produce suckers; branch crotches are often narrow, splitting easily in storms. Still, elms are widely planted, valued for their fast growth, moderate shade, and environmental toughness. Researchers continue to devote much effort to finding disease-resistant selections. All elms are fairly soil tolerant, have handsome oval leaves.
U. alata. WINGED ELM. Deciduous. Native to the Southeast. To 2040 ft. tall, not quite as wide. Open, airy canopy. Leaves 1212 in. long, finely toothed, dark green turning pale yellow in fall. Common name derives from corky outgrowths (wings) on twigs and young branches. Degree of winging varies among seedlingsthe wings stand out on some, while on others they're almost nonexistent. Your best bet is to get a cutting-grown tree from a parent with good bark characteristics. Small red spring flowers are followed by small reddish seeds. 'Lace Parasol' is a weeping form (to 8 ft. tall, 12 ft. wide after 45 years).
U. americana. AMERICAN ELM. Deciduous. Native to eastern North America. This majestic tree once graced lawns and streets throughout its range, but its ranks have been decimated by Dutch elm disease. Grows fast to 100 ft. tall, with equal or greater spread. Prized for its high, arching branches, which create a beautiful, symmetrical canopy. Dark green, tooth-edged, pointed-oval leaves are 36 in. long and rough to the touch; they turn yellow in fall, with the intensity of the color varying from tree to tree. Small red flowers in early spring. Easily transplanted. Tolerates wet, alkaline, and saline soils.
A long search for American elms resistant to Dutch elm disease has culminated in a number of improved selections. Probable hybrid 'Jefferson' has dark green leaves that emerge earlier and are retained later. 'New Harmony' is broadly V-shaped, often with gracefully drooping branch tips. 'Valley Forge' grows into a dense, broad, upright vase shape; it is considered the most disease-resistant selection. Moderately resistant 'Princeton' forms a broad umbrella.
U. crassifolia. CEDAR ELM. Deciduous; semievergreen in extreme South Texas. Native from Texas to Mississippi and northern Mexico. Fairly fast growth to 5075 ft. tall and 4060 ft. wide. Stiff, shiny, dark green leaves to 2 in. long, rough to the touch; they turn burnt yellow or gold in autumn. Twigs and branches (like those of U. alata) have corky wings. Tiny flowers in late summer. Well adapted to alkaline soils. Little to moderate water.
U. parvifolia. CHINESE ELM, LACEBARK ELM. Semievergreen or deciduous, depending on winter temperature and particular selection. The best elm for home gardens and an excellent shade or lawn tree. Fast growth to 4060 ft. tall, 2540 ft. wide. Extremely variable in form, but generally rounded, with long, arching, pendulous branchlets. On older trees, bark flakes off in patches, creating a beautifully mottled combination of gray, green, orange, and brown. Leathery dark green leaves are 34 to 212 in. long, broadly oval and pointed, evenly toothed; may turn yellow to reddish orange in fall. Tiny red flowers from late summer to autumn. Resistant to Dutch elm disease, elm leaf beetle, and Japanese beetle. Drought tolerant.
Forms that hold their leaves are often sold as 'Sempervirens', but that is not a valid name. Two more or less evergreen selections popular in the Coastal South (USDA 9) are 'Drake' and 'True Green'; they are not as cold hardy as others and are not recommended for the Upper or Middle South (USDA 6-7). Selections with particularly showy exfoliating bark include 'Allee', a vase-shaped tree to 70 ft. tall, 60 ft. wide; 'Athena', a lower, wide-spreading tree to 40 ft. tall, 55 ft. wide; 'Bosque', oval tree with strong central leader, 4050 ft. tall and wide; 'Burgundy', a rounded tree to 18 ft. tall, 20 ft. wide after eight years, with burgundy fall color; 'Everclear', columnar, 40 ft. tall, 15 ft. wide; and 'Milliken', an oval to rounded tree to 50 ft. high, 40 ft. wide. Numerous dwarf and compact selections, such as 'Hokkaido', are popular for bonsai.
to 18 ft. tall, 20 ft. wide after eight years, with burgundy fall color; 'Everclear', columnar, 40 ft. tall, 15 ft. wide; and 'Milliken', an oval to rounded tree to 50 ft. high, 40 ft. wide. Numerous dwarf and compact selections, such as 'Hokkaido', are popular for bonsai.
A word of caution: A vastly inferior species, U. pumila, Siberian elm, is sometimes sold as Chinese elm.