The structural elements of a garden create the garden's foundation - an underlying sense of formality or informality, flamboyance or subtlety, ordered geometry or fascinating fluidity. These basic elements can then be developed into a finished landscape by the details of specific plantings and, frequently, garden ornament. We often think of the garden's structure as resting on "hardscape": stone walls, brick patios, curving pools, paved paths, and other gardener-constructed features made from non-plant material. However, a garden's structure need not be created by hardscape alone, and in fact, gardens with excellent structure can be created using no hardscape at all, but instead, relying on a diverse array of plant materials to create living structural dimension. A garden whose structure is built by plants depends on very careful plant selection for the structure to give the garden its needed anchor in the landscape. However, this is not as difficult as it may seem, and, in fact, is often more successful than imposing arbitrarily chosen hardscape on a garden without appropriate consideration of the nature and needs of an individual garden site.
The palette of plants useful for the creation of structure in the garden is as extensive as the list of plants grown in any given area. There are certain foundation plants, however, which can be relied upon to give consistent, year-round, structural dimension in the landscape and are often included in a garden just for that purpose. Two such plants are Common Boxwood, Buxus sempervirens, from northern Africa and southern Europe, and Littleleaf Boxwood, Buxus microphylla, from Japan and Korea. Ironically, gardeners on both sides of the Atlantic make ardent statements about the famous 'English Box' or 'American Box' when neither of the horticulturally important species is native to either England or America. English Boxwood is Buxus sempervirens 'Suffructicosa', the slow-growing, mounding, fine textured shrub of Old England, while American Boxwood is B. sempervirens 'Arborescens', a somewhat more coarse textured form that will eventually reach tree proportions (hence the name 'Arborescens', meaning tree-like).
Boxwood is one of the oldest known garden plants with records of its use dating back to 4000 B.C. in Egypt. Historically, Boxwood has been the traditional plant of formal English gardens and many French Parterre gardens. It has been very important in early American formal gardens, such as those seen restored in Williamsburg, VA and preserved at a number of historically important Presidential homes and gardens. But Boxwood is not only a historical plant, it offers a great deal to modern gardens both in formal and informal roles.
Both Boxwoods are relatively slow-growing, evergreen shrubs with a refined, billowy habit created by dense, fine textured foliage. The dark, rich green leaves of Boxwood are only 1/4 to 1 inch long and half as wide, but there are so many leaves packed very closely, that the plants appear to have a nearly continuous surface from even a short distance away. They are both hardy throughout the southeastern U.S., from the coast to the mountains, but may show some winter burn in severe mountain winters, especially if grown in a sunny site. There is some variation in hardiness among the numerous cultivars, with some exceptions noted below among the brief cultivar descriptions. Boxwood generally prefers partial shade with moist, well-drained soils and cool roots, however, it can also do well in clay soils and full sun when care is taken to avoid droughty conditions.
Boxwood is a reasonably adaptable plant but it is subject to some pest and disease problems best dealt with by keeping the plants as healthy and vigorous as possible (with the realization that individual plants may need replacing after a decade or so). Some of these potential problems include nematodes and root rot which can gradually kill the root system. This is usually indicated by orange or rusty colored foliage in one area of the plant (where the analogous roots are in trouble). Various insects also attack the foliage. Regional extension agents can help with appropriate control measures if pests become serious problems. In general, if Boxwood is sited well, pests and diseases are not serious and the plants remain beautiful for the extent of their long life. Boxwood is readily propagated from cuttings taken any time of the year and rooted under mist. It can also be propagated from seed but named cultivars are superior to seedlings and so should be the choice for modern gardens.
There are a huge number of cultivars grown of both species with a broad range of sizes and shapes, and including some variegated forms. One way to tell Common Boxwood from Littleleaf Boxwood is by the somewhat unpleasant odor of Common Boxwood foliage and stems when bruised. Perhaps the most extensive collection of Boxwood cultivars available in the country for public viewing can be found at the University of Virginia Blandy Experiment Station in Boyce, Virginia. There is also an extensive collection of cultivars at the National Arboretum in Washington, D.C. For those especially interested, the American Boxwood Society, Box 85, Boyce, VA 22620 (703-939-4646) has detailed publications available and issues a quarterly publication, The Boxwood Bulletin, for members. Some of the most interesting forms and cultivars that have performed well in the Piedmont conditions at The NCSU Arboretum (now the JC Raulston Arboretum) are described below.
A few good cultivars of Littleleaf Boxwood include 'Helen Whiting' named after a well-known plantswoman and Boxwood afficionado with beautiful, excellent quality foliage, 'Kingsville Dwarf', a very low growing form that can be sheared to make an interesting, tall groundcover, 'Morris Midget', a dwarf, formally round cultivar with light green foliage and very slow growth that is an excellent choice for a formal townhouse garden (or any other use requiring a horticultural 'pom-pom'), 'Sunnyside' with probably the largest leaves of the Littleleaf Boxwood forms and a unique texture for this group (but it suffers from winter bronzing in full sun sites), and 'Wintergreen', an especially hardy form (will grow well as far north as Chicago!) with emerald green foliage and very uniform habit that makes a good choice for a low formal hedge. Two frequently found botanical forms of Littleleaf Boxwood are B. microphylla var. koreana, the Korean Box, an exceptionally hardy form reaching 2 to 2 1/2 feet whose leaves are somewhat inrolled at the margins, and B. microphylla var. japonica, the Japanese Box, which is particularly well-adapted to the southeastern U.S. as it has good heat tolerance and some resistance to root rot and nematodes.
Some recommended cultivars of Common Boxwood are 'Aureo-variegata' with yellow variegated foliage, 'Bullata', that eventually reaches 8 feet in height with interestingly blunt, shortened leaves, 'Elegantissima', a slow growing form with striking, cream variegated foliage that is a spectacular specimen plant with time but is not the best choice for other uses, 'Glauca' with a blue bloom to the foliage, 'Graham Blandy' with an extremely narrow and columnar habit and beautiful grey-green foliage (two plants of 'Graham Blandy' flank the visitors center entrance at The NCSU Arboretum (now the JC Raulston Arboretum)), 'Myrtifolia', with especially small, neat foliage, 'Pendula', with some weeping character, 'Pullman', with rich green foliage, rapid, vigorous growth and exceptional cold hardiness, 'Pyramidalis' with a handsome, softly pyramidal shape and 'Welleri' with a broad, rounded habit and good winter foliage color.
The cultivars listed above are only a handful of the excellent cultivars available in the trade. For many years, the standard for 'edging and hedges' was B. sempervirens 'Suffructicosa', the "English Box". For example, wonderful old plantings of English Boxwood can be found on the grounds of the Lincoln Memorial in Washington, D.C. But there are many other cultivars available with better hardiness, disease and insect resistance, and unique color or form, that deserve greater attention in the landscape, especially for use as quality foundation plants.
At The NCSU Arboretum (now the JC Raulston Arboretum), an extensive planting of Boxwood selections, both young and more mature, adds quiet structure to the Southall Memorial Garden adjacent to the brick house. A visit to the Southall garden will show how Boxwood can be a beautiful component of a garden's foundation.