The Buxus genus includes about 70 species of slow-growing broadleaf evergreens. Most of the garden forms are cultivars or hybrids of two species— B. sempervirens (common box) and B. microphylla (Japanese box). Boxwoods are typically large shrubs or small trees, but most of the varieties used in modern landscaping are dwarf varieties, such as B. sempervirens 'Suffruticosa', a popular plant 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). These dwarf boxwood shrubs are prized for their densely packed, light-green leaves and rounded, compact growth habit.
|Botanical Name||Buxus spp.|
|Common Names||Boxwood, English boxwood, box|
|Plant Type||Broadleaf evergreen shrub|
|Mature Size||Varies by species; dwarf varieties are typically 2 to 8 feet tall|
|Sun Exposure||Full sun to part shade|
|Soil Type||Medium moisture loamy soil|
|Soil pH||6.8 to 7.5|
|Bloom Time||April to May|
|Flower Color||Green to creamy yellow (flowers are not significant)|
|Hardiness Zones||5 to 9 (depends on species and variety)|
|Native Area||Southern Europe, Asia|
How to Grow Boxwood Shrubs
Boxwoods are best planted in loamy soil in a full-sun to part-shade location, preferably in an area somewhat sheltered from winds. Their roots are shallow, so the soil must be protected from the heat. Maintain a layer of organic garden mulch, three 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 one foot outwards, around the whole circumference, space permitting.
When grown as a hedge or formal screen, the primary maintenance for the shrubs will be in regular pruning, though this will not be necessary if you are using them as specimen plantings.
Boxwoods will 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. When sheltered by trees, the roots of dwarf boxwoods will profit from the cooler soil temperatures.
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.
For the first two years, boxwoods require deep weekly watering. Avoid shallow watering, since moisture will not reach the deepest roots. Mature plants will thrive with a deep watering every 2 to 4 weeks.
Temperature and Humidity
Boxwoods typically thrive in the climate conditions in zones 6 to 8. In very hot summer weather, the shrubs will appreciate more water and shade. Zone 5 gardeners may find that stem tips die back in cold weather.
Fertilize with an all-purpose fertilizer in spring prior to the emergence of new growth.
Propagating Boxwood Shrubs
Boxwood is best propagated by rooting some stem cuttings. In midsummer, cut 3- to 4-inch lengths of stem tips of new growth. Remove the lower leaves and scape the bark from one side of the cutting. Bury the ends of the cuttings in a pot filled with a mixture of sand, peat moss, and vermiculite. Moisten the potting medium, place the pot in a sealed plastic bag, and set it in a bright location. Check the moisture daily, and mist whenever the cutting is dry. Check for roots every few days by tugging on the cutting.
When the roots are sufficiently developed, remove the pot from the plastic bag and transplant the cutting into another container filled with a rich potting mix. Continue to grow the plant in a sunny window until outdoor planting time the following spring.
Pruning Boxwood Shrubs
Although they are known for their tolerance for hard pruning, most boxwoods will form a nice informal shape without much pruning at all. Only occasional pruning is required to clean out dead branches or those that are twisted together.
When pruning hard for shape, the trimming can be done almost any time during the growing season, though it should be avoided in late fall to avoid winter bronzing.
Varieties of Boxwood
There are many kinds of boxwoods, and the best plant for you depends on your particular landscaping needs.
- Buxus sempervirons 'Suffruticosa' cultivars are favored in gardens because they grow more slowly. The growth habit is tighter and more compact than the 'Arborescens' cultivars. These shrubs grow to 2 to 3 feet in height with a 2- to 4-foot spread.
- B sempervirens' Arborescens' is a considerably larger, faster-growing plant, growing as tall as 20 feet with a spread of 8 to 10 feet.
- B. sempervirens 'Monrue Green Tower' is a columnar form, 9 feet tall and 1 to 2 feet in spread. It is great for a tall screen or for sculpting topiary use. Two plants can be used to flank an entryway.
- Buxus microphylla var. japonica, the Japanese boxwood, is one of the most popular shrubs for low hedges. It is also preferred 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.
- B. microphylla japonica 'Winter Gem' is 4 to 6 feet tall with a similar spread. The cultivar name comes from the pleasing gold and bronze tinges of its foliage in winter.
- B. microphylla japonica 'Golden Triumph' is 2 to 3 feet tall and 3 to 4 feet wide; it is valued for its variegated leaves.
A common problem for boxwood shrubs is "winter bronzing," a shift to reddish-brown or yellowish foliage color caused by winter exposure to wind and sun. One way to address the problem is to spray an anti-desiccant on the shrubs in late November and again in late January and to make sure your plants are watered sufficiently throughout the growing season. Also, you can build a structure around your bushes to shelter them from the wind and sun in winter. But some gardeners do not mind—or even actually value—the winter bronzing on the foliage.
Leafminer, boxwood mite, and boxwood psyllid are common pests. The damage is disfiguring but not fatal, and the pests can be treated with horticultural oils. In the deep South, nematodes are of concern.
Boxwoods can be susceptible to fungal blights and leaf spot, and root rot can also be a problem in poorly-drained soils.
In the northern part of the hardiness range, new growth is susceptible to winter damage.
Toxicity of Boxwood
All parts of a boxwood plant are toxic and can cause nausea, vomiting, diarrhea, convulsions, and even respiratory failure if ingested. But ingestion is rare, as this plant has no attractive berries and the leaves are not tasty.
Wear gloves when handling or pruning the plants, as touching them can cause minor skin irritation.
While people occasionally use boxwood shrubs as specimen plants 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.
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.