Culture
Buxus sempervirens is typically grown in evenly moist, well-drained loams (e.g., sand-clay mixture) in full sun to part shade. Plants will grow well in a variety of part shade situations, including open sun-dappled conditions or light shade with several hours of morning sun or early afternoon sun. Plants can grow in close to full shade, but typically are less vigorous and more open with decreased foliage density. When grown in full sun, plant foliage is more likely to scorch, bronze in winter or suffer from mite attacks. Plants prefer soils with a pH of slightly acidic to slightly alkaline. Plants are generally tolerant of pruning and shearing. Pruning should never be done prior to the last spring frost date. Pruning too early in spring often promotes tender new growth that may be damaged or killed by a late spring frost. Avoid cultivating around plants because they have shallow roots. Roots appreciate a good organic (e.g., bark or compost) mulch (1-2”). Thin plants and remove dead/damaged branches annually to improve air circulation. Boxwood is best sited in locations sheltered from strong winds, with, if possible, some protection from full winter sun. Foliage may bronze in winter when exposed to half day to full day sun. Winter winds can remove moisture from leaves at a rapid rate, often resulting in dehydration and bronzing. Species plants are easily propagated by cuttings or seed.
Noteworthy Characteristics
Buxus sempervirens is a rounded to broad-rounded shrub or small tree that is native primarily to open woodlands and rocky hillsides in southern Europe, northern Africa and western Asia. It typically matures in a shrubby form to 5-15' tall, but may grow as a tree to as much as 20-30' tall. Small, elliptic to oval to oblong leaves (1/2" to 1 1/2" long) are simple, opposite, smooth-margined and evergreen. Leaves are dark glossy green above and yellowish-green below. Inconspicuous, apetalous flowers in axillary clusters are pale green to yellow to creamy white. Flowers appear in April and May. Fruit is a dehiscent capsule (to 1/3" long) that matures to brown.
Genus name comes from the Latin name for plants in this genus.
Specific epithet means always green in obvious reference to the evergreen foliage.
Common name of boxwood is in reference to the prior use of the wood to make boxes. Another theory on common name is that the name is in reference to young plant stems which are quadrangular (square box cross section).
'Henry Shaw' is a dense, pyramidal-rounded cultivar that typically grows to 3-4' tall over the first 20 years. It is a slow-growing evergreen shrub that may eventually mature to as much as 6-7' tall. Oval dark green leaves (to 7/8" long) may acquire bronze tones in winter. Cultivar name honors Henry Shaw (1800-1889) who founded the Missouri Botanical Garden in 1859.
Problems
Boxwood can be somewhat temperamental to grow in the St. Louis area where its evergreen foliage tends to bronze (turn unattractive brownish-yellow) in harsh winters, particularly if plants are located in open areas exposed to full sun and winter winds. Otherwise, boxwood requires little special care other than annual pruning. Susceptible to boxwood blight and leaf spot diseases. Root rot can also be a problem in poorly-drained soils. The three main insect pests of boxwoods are boxwood leafminer, boxwood mite and boxwood psyllid. In the deep South, nematodes are of concern. New growth is particularly susceptible to winter damage. Rabbits and deer tend to avoid this plant.
Uses
Vertical specimen or accent for foundation plantings, formal gardens, Mediterranean gardens, mixed beds and borders, and large containers. Suitable for use as a topiary. Mass to create a narrow hedge.