Native to southern Europe, western Asia and northern Africa, the boxwood shrub (Boxwood spp.) is widely planted in cultivated landscapes. It is classified as a shrub but can also be trained to grow as a small tree. Although hardy to U.S. Department of Agriculture Zone 5, it is still subject to winter kill in all areas of that plant hardiness zone. Even though it is slow growing, averaging less than 12 inches of new growth per year, boxwood often is the shrub of choice planted to create living fences, topiary or defining borders in the landscape.
Boxwood can grow to a height of 10 to 15 feet, although it thrives if kept shorter because it takes well to pruning and training. Its 1-1/2 inch long, oval, evergreen leaves are dark green on their tops and yellowish-green with a white line on their undersides. Specimens left to grow without extensive pruning or shearing develop an overall gumdrop shape.
Happiest in partial shade, boxwoods also will grow in full sun as long as the soil is well-drained. Boxwoods cannot survive long in soil that retains water. Keep them away from the drip line of trees and the eaves of buildings. Boxwoods can tolerate soils that are slightly acid or slightly alkaline but grow best in soil with a fairly neutral pH level.
Although 30 or more species of boxwoods are known, only two are widely cultivated: common boxwood (Buxus sempervirens) or littleleaf boxwood (B. microphylla). Common boxwood is the more common of the two, growing to a height of 10 to 15 feet. Littleleaf boxwood is lower-growing, reaching only about 4 feet high with an equal spread. Unlike the common boxwood, littleleaf boxwood has bright green leaves that are only 1/4 to 1 inch in length.
Care and Culture
Naturally shallow-rooted, care must be taken not to plant boxwoods too deeply or the plants will perish. The top one-eighth of the rootball should be above the soil line, according to Clemson University Extension. Because they are so shallow-rooted, boxwoods benefit from the application of a 3-inch mulch. Do not use a deeper mulch as the roots may develop too close to the soil line.
Prune boxwood in June to remove dead or diseased wood and to shape the plant. To encourage branching, shear off new growth of newly-planted boxwood several times during its first two growing seasons. This will help the plants fill in and create a dense hedge.
Fertilize in spring by sprinkling granulated fertilizer near the base of the plant, about 6 inches out from the main stem. Keep the fertilizer from touching the base of the plant.
Pests and Diseases
Several insects and diseases affect boxwoods, including boxwood psyllid, boxwood mite, boxwood leaf miner, Phytophthora root rot, as well as foliage and twig blights. Winter sunscald is prevalent in colder areas. Protect boxwood by surrounding it with snow fencing wrapped in burlap to keep it out of the winter sun. Do not let the burlap touch the plant, according to the Virginia Cooperative Extension.