English boxwood shrubs have long been symbols of upscale properties. They're wonderful for those formal landscapes with lots of straight lines and patterns. Because that refined, geometric style comes at the cost of high maintenance, most gardeners nowadays prefer the more relaxed cottage-garden style. But there are still some specialized uses for these old-time favorites that modern gardeners should know about.
Taxonomy and Botany
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.
English boxwood shrubs are prized for their densely packed, light-green leaves and rounded, compact growth habit. These plants will reach three feet at maturity (with a slightly greater spread). True dwarfs, Suffruticosa English boxwood shrubs are slow-growing plants that are easily shaped by pruning, which is a desirable trait for hedges and topiaries. Another dwarf variety is the Korean (Buxus sinica var. insularis). It reaches a mature height of just two feet tall (with a slightly greater spread).
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, three inches thick, around each plant. Start mulching two 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 one foot outwards, around the whole circumference, space permitting. Fertilize in spring prior to the emergence of new growth (an all-purpose fertilizer is sufficient).
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.
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. Plants are already deprived of water in winter by the fact that water is locked up in the frozen ground, a problem that is made worse by the drying influence of exposure to wind and sun.
One way to address the problem of winter bronzing on these dwarf boxwood shrubs is to 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.
But sheltering these plants (like trimming them) is an operation done 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.
These dwarf boxwood shrubs can be grown in USDA plant hardiness zones 6 to 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 to 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.
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. They respond well to pruning, which makes them popular as knot-garden plants, as topiary plants, and as bonsai plants. Wall germander (Teucrium chamaedrys) is used in a similar way.
Name Origin and History
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 in such gardens 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. B. sempervirens Arborescens is for zones 5 to 8; it's a tall type (8 to 12 feet in height, with a spread of 8 to 10 feet).
A third boxwood widely encountered is Buxus microphylla japonica, the Japanese boxwood, which is preferred in areas where a more drought-tolerant shrub is needed. It is for zones 6 to 9 and has mature dimensions of 6 to 8 feet tall by 10 to 15 feet wide. Japanese boxwoods figure prominently at a number of historic sites in the Far East.
Other Types of Boxwoods
There are many kinds of boxwoods, and the best plant for you depends on your particular landscaping needs. Other types (all suited to zones 5 to 9) of note include:
- B. microphylla japonica Winter Gem: four to six feet tall and wide; cultivar name comes from the pleasing gold and bronze tinges its foliage gets in winter
- B. microphylla japonica Golden Triumph: two to three feet tall and three to four feet wide; valued for its variegated leaves
- B. sempervirens Monrue (sold under the name of Green Tower): nine feet tall by one or two feet wide; severely columnar form makes it great for sculpting topiary or for use where space is limited (grow two to flank an entryway, as you would with Sky Pencil holly)