Poplars may be popular out West, but in the South they're proble- matic. They're messy, pest and disease prone, weak wooded, and short lived. Their aggressive surface roots crowd out other plants, invade water lines, and crack pavement. Cut or disturb the roots, and they'll sucker profusely. If your yard already has a poplar, leave it or remove it, but don't ever plant one unless you live in West Texas. (This warning does not apply to tulip poplar [Liriodendron tulipifera], which belongs to a different genus and makes a fine shade tree.)
Some poplars are beautiful or distinctive enough that people buy them despite their liabilities. Several have good fall color. Leaves of most poplars are roughly triangular, sometimes toothed or lobed. Pendulous catkins appear before spring leaf-out; those on male trees are denser textured. Female trees later bear masses of cottony seeds that blow about and become a nuisance; for that reason, male (seedless) selections are offered in garden centers. Deer don't usually browse poplars.
P. alba. WHITE POPLAR. Zones US, MS, LS; USDA 6-8. Native to Europe, Asia. Broad, widespreading tree to 4060 ft. tall and wide. Leaves are dark green above, white and woolly beneath, 25 in. long, usually with three to five lobes. A lively tree even in light breezes, with flickering white and green highlights. Poor fall color. Tolerates a wide range of soils. Suckers profusely. A seedless selection, P. a. pyramidalis, called Bolleana poplar (and often sold as P. bolleana), forms a narrow column; it has a white trunk like that of birch (Betula).
P. deltoides. EASTERN COTTONWOOD. Zones US, MS, LS, CS; USDA 6-9. Native from Quebec to Florida and Texas. Grows very fast in moist soils, quickly reaching 30 ft. tall; eventually reaches 75100 ft. tall, up to 70 ft. wide. Provides fast shade and tolerates wet sites, drought, salt spray, acid and alkaline soils, and winter cold, but not good in gardens because of its huge size, short life, and tendency to break up in storms.
P. fremontii. WESTERN COTTONWOOD, FREMONT COTTONWOOD. Zones US, MS, LS, CS, TS; USDA 6-11. From California and Arizona. The cottonwood of desert water holes and watercourses. To 4060 ft. or taller, about 30 ft. wide, with 2- to 4-in.-wide, thick, coarsely toothed, glossy, yellow-green leaves that turn bright lemon-yellow in fall. Does well in West Texas. 'Nevada' is a male selection. P. f. wislizenii, Rio Grande cottonwood, is similar but has slightly larger leaves. It is well adapted to arid regions; its native range is from southern Colorado to northern Mexico.
P. nigra 'Italica'. LOMBARDY POPLAR. Zones US, MS, LS, CS; USDA 6-9. Male selection of a European species. Lovely columnar tree to 40100 ft. tall, 1530 ft. wide, with upward-reaching branches. Bright green, 4-in. leaves turn a beautiful golden yellow in autumn. However, it's subject to a canker disease that will soon kill it. Upright English oak (Quercus robur 'Fastigiata'), a more permanent tree, is a good substitute.
P. tremuloides. QUAKING ASPEN. Zones US, MS; USDA 6-7. Widely distributed in North America; native to northern latitudes and mountains. Takes poor soil; generally performs poorly or grows slowly at low elevations. To 4050 ft. tall, 2030 ft. wide; often grows with several trunks or in a clump. Smooth, pale gray-green to whitish bark. Dainty, round, 2- to 4-in., light green leaves flutter and quake with even the slightest movement of air. Brilliant golden yellow autumn foliage. Apt to suffer from sudden dieback or borers. 'Prairie Gold', to 40 ft. tall and 15 ft. wide, was bred to tolerate lowland conditions and resist disease.