The hot, humid summers and mild winters of the American South (USDA Hardiness Zones 7 through 9 predominantly) require gardeners to choose resilient plants for creating screens or tall hedges. Many evergreen plants thrive in this area for good year-round screening. Avoid planting canker-susceptible plants like Leyland cypress, fungal-ridden red-tip photinia or ecologically invasive ligustrum.
Two species of arborvitae successfully create evergreen screens in southern landscapes. The American arborvitae (Thuja occidentalis) grows best in USDA Zone 7 in the South. Dozens of cultivars or hybrids exist with varied foliage colors, mature plant heights and tolerances to heat or drought. The Oriental arborvitae (Platycladus orientalis) prospers in warmer areas of the South in fertile and lean sandy soils alike. It provides cultivars with blue-green or yellow-green foliage choices.
Evergreen hollies grow well across the South in soils that do not become soggy. Whether you choose varieties that are female-flowering and display decorative fruits, or male-flowering ones that remain evergreen, many species and hybrids afford gardeners many landscape choices. Some species commonly grown include dahoon (Ilex cassine), Chinese holly (Ilex cornuta) as well as hybrid varieties like 'Nellie R. Stevens,' 'Mary Nell,' 'Hohman,' 'San Jose,' 'Wirt L. Winn,' 'Emily Brunner' and 'James G. Esson.' These hollies typically are used in landscapes across USDA Zones 7 through 9.
Many deciduous viburnum shrubs (Viburnum spp.) make nice, rather fast-growing and dense screening plants, but often it's the large-leaved or evergreen species that are favored for screening. Awabuki viburnum (Viburnum awabuki and variety 'Chindo'), laurustinus (Viburnum tinus), sandankwa (Viburnum suspensum), and sweet viburnum (Viburnum odoratissimum) grow nicely in the South in USDA Zones 8 and 9.
University of Georgia horticultural expert Dr. Michael Dirr attests to the fact that cherrylaurels make dull green walls, but are nonetheless effective and long-lived screening hedges. Although birds eat the black fruits and cast seeds across the landscape, both Carolina cherrylaurel (Prunus caroliniana) and the common or English cherrylaurel (Prunus laurocerasus) and their cultivars develop dense masses of evergreen leaves. Carolina cherrylaurel grows well in all reaches of the South, including southern Florida.
In mild winter parts of the coastal South, podocarpus remains hardy and evergreen, becoming a fine-textured, upright shrub for screening. Choose cultivars of three species: Podocarpus macrophyllus, Podocarpus salignus, and Podocarpus nagi (this plant's botanical name recently changed to Nageia nagi.) Use it in USDA Zones 9 and 10, and perhaps also in the warmest areas of Zone 8.
In USDA Zones 7 and 8 where soils are fertile, moist and well-draining, plant false cypresses (Chamaecyparis spp.). Growing tall into trees, these need tip pruning to keep them under 20 feet. If soils are well-draining and hot, consider the Arizona cypress (Cupressus arizonica), especially in windy locales. Expect this species to be rather short-lived when humidity is high and soil is wet through the summer and winter.
Although also commonly called cleyera, the Japanese ternstroemia (Ternstroemia gymnanthera) makes a fine alternative to the fungus-prone red tip photinia once widely grown across the South. Perhaps the prettiest feature of these evergreen shrubs revolves around the red to pink-tinted new foliage. The many cultivars of this species grow well across most of USDA Zones 7 through 9.