Taxonomy and Botany of Dwarf Boxwood Shrubs
Plant taxonomy classifies dwarf boxwood shrubs (English variety) as Buxus sempervirens. The cultivar is 'Suffruticosa.' English boxwoods are evergreen shrubs. These bushes are also categorized as broad-leaf evergreens.
Characteristics of These Bushes
English boxwood shrubs are prized for their densely packed light-green leaves and rounded, compact growth habit. This plant will reach 3 feet at maturity. A true dwarf, 'Suffruticosa' English boxwood shrubs are slow-growing plants that are easily shaped by pruning -- a desirable characteristic for hedges and topiaries, as we will see below. Another dwarf variety is the Korean (Buxus sinica var. insularis). It reaches a mature height of just 2 feet tall.
Plant Care Facts
Pruning (shearing) is done for aesthetic purposes, but as a practical issue, remember to mulch English boxwood shrubs. Their roots are shallow, so they must be protected from the heat. Maintain a layer of organic garden mulch, 3 inches thick, around each plant. Start mulching 2 inches out from the trunk (as a general rule, it is bad to mulch right up against the trunk of a bush or tree, because it invites pests and diseases), and work your way about 1 foot outwards, around the whole circumference, space permitting. Fertilize in spring prior to the emergence of new growth (an all-purpose fertilizer is sufficient). For winter care, see below.
By far, the primary maintenance in growing a group of these bushes as a hedge will come in the form of keeping the hedge trimmed neatly. Fortunately, these plants are deer-resistant shrubs, so you usually do not have to worry about Bambi doing the "trimming" for you.
USDA Plant Hardiness Zones, Sun and Soil Requirements
These dwarf boxwood shrubs can be grown in zones 6-8. The Korean type is a bit more cold-hardy and better-suited to gardeners in zone 5.
English boxwood shrubs require well-drained soils, or they will suffer from root rot. Although they may tolerate soils with a lower pH, certified soil scientist, Victoria Smith notes that they prefer a soil pH in the 6.8-7.5 range. They'll take full sun to partial shade, but planting them in an area bathed in dappled shade for the hottest part of the afternoon is preferable. For, when sheltered by trees, the roots of dwarf English boxwoods will profit from the cooler soil temperatures.
Uses for Dwarf Boxwood Shrubs in Landscape Design
While people occasionally use English boxwood shrubs as specimens in their landscape-design work, they are more often grouped together in foundation plantings or to form hedges. Dwarf boxwoods are famous for their use in formal landscape design. Their amenability to pruning makes them popular in knot gardens and as topiary and bonsai plants. Other uses for these bushes extend beyond the life of the plant. As a cut evergreen for the holiday season, sprigs of it are used in wreaths, garlands, kissing balls and topiary "tree" arrangements.
History, Types, Winter Care
Outside of the U.S., boxwood shrubs are generally referred to simply as "box." Indeed, the ancient Greeks and Romans used the wood to make decorative boxes (the Buxus in their scientific name means, "box" in Latin).
English boxwood shrubs are found not only in the colonial gardens of Williamsburg, Virginia, but also at the White House. Those of the 'Suffruticosa' cultivar are favored over their cousins, Buxus sempervirens 'Arborescens,' because they grow more slowly, and the growth habit of the dwarf English boxwoods is tighter and more compact. A third boxwood widely encountered is Buxus microphylla ssp. japonica -- Japanese boxwood, which is preferred in areas where a more drought-tolerant shrub is needed.
A common problem for English boxwood shrubs is "winter bronzing," manifested by a change in foliage color to a reddish-brown or yellowish. It is the result of exposure in winter to wind and sun. Such exposure causes a water loss that damages the foliage. Remember, plants are already deprived of water in winter by the fact that water is locked up in the frozen ground, a problem that is just exacerbated by the drying influence of exposure to wind and sun.
How should you address the problem of winter bronzing on these dwarf boxwood shrubs? First of all, spray an anti-desiccant on them in late November and again in late January, and make sure your plants are watered sufficiently throughout the growing season. Also, build a structure around your bushes that will shelter them from the wind and sun in winter.
Note, however, that sheltering these plants -- like trimming them (see above) -- is an operation taken for aesthetic, not practical reasons. Winter bronzing does not kill English boxwood shrubs. Some gardeners do not mind (or even actually value) the winter bronzing on the foliage. But other gardeners consider it unsightly. Normal green foliage should, however, return in spring on the new growth of these small evergreen shrubs; just prune out the damaged foliage at this time if you feel that its presence mars the appearance of the plants.