Evergreen Oaks: Hearty Trees for the South
Evergreen oaks in North Carolina were traditionally almost entirely used in the coastal plain, lower piedmont and Sandhills. Although typically described as being adapted to USDA hardiness zones 6 through 9, their performance and growth rate is by far better in warmer climates. One way to interpret the effects of hardiness zones on evergreen oak performance is to observe the height and width range of various species in addition to growth rates. Outside of a species’ optimum climate and hardiness zone, expect the lesser size and growth rate.
The smallest of the evergreen oaks is the Japanese oak (Quercus acuta), which ranges from 20 to 30 feet tall and 15 to 20 feet wide. Our largest evergreen oak is the native live oak (Quercus virginiana), ranging from 40 to 80 feet high and spreading 60 to 100 feet wide. In between these two species are the blue Japanese oak or ring-cupped oak (Quercus glauca), Chinese oak (Quercus myrsinifolia), ubame or ubamegashi oak (Quercus phillyraeoides), Monterrey oak (Quercus polymorpha), and the Mexican oak (Quercus rysophylla).
A variant of the ubame oak has been assigned the cultivar name ‘Emerald Sentinel.’ Michael Dirr favors this one for its hardiness and offers these comments: “Introduced by the JC Raulston Arboretum in North Carolina for its upright habit, fast growth, showy catkins, and ease of rooting.” The leaves are quite handsome because the new growth emerges as a bronze red color. It demonstrates excellent tolerance to heat and drought.
Evergreen oaks, especially the small ones, have potential for greater use in the landscape as specimen trees, screens and windbreaks. Wildlife observers will enjoy their presence as habitats for turkey, deer, ducks, quail and song birds. Expect some minor but not life-threatening problems from pests. As with many oaks, expect to see leaf spots, galls, scale, cankers, caterpillars and possibly mistletoe. In areas with snow and ice accumulations, you may see excess limb breakage because of heavy foliage.
Visit the JC Raulston Arboretum to see a variety of evergreen oak species.