Boxwood

Boxwood (Buxus species) are popular for formal gardens.
Barbara H. Smith, © 2022 HGIC, Clemson Extension

Boxwood has long been a cornerstone of southern gardens, especially on historic estates in the Lowcountry of South Carolina. They are ideal for formal gardens with their dense growth habit that allows them to be pruned into hedges, rounded shrubs, and topiaries. Today, more than 90 species and 260 cultivars of boxwood are available. Littleleaf, Japanese, American (including English), Korean, and hybrids are the most widely grown boxwood.

Growth Rate

Boxwood grow at slow, moderate, and fast rates. Dwarf cultivars grow at a slow rate and rarely require pruning. Cultivars that grow at a moderate rate may require annual pruning after they have established to maintain their desired size and shape. Boxwood cultivars with a fast growth rate will reach their desired height quickly and require pruning once or twice a year to maintain that height.

Landscape Use

Boxwood can have many natural forms, such as round, mounding, columnar, pyramidal, etc. Because of their versatility, boxwood can be used as foundation plantings, to separate or screen areas, as a background for other plantings, to provide a framework of a formal garden, and to edge a terrace, walkway, or parking area. Boxwood can also be used in containers and even as bonsai.

Cultivation

Light: Boxwood grow best in part shade. They can tolerate morning sun so long as they have afternoon shade. Korean boxwood is the most sun-tolerant boxwood. Boxwood grown in full sun are more likely to have cold damage in the winter.

Soil: The ideal soil pH for boxwood is 6.8 to 7.5, which is neutral to slightly alkaline. Most can tolerate a slightly lower pH. Have the soil tested to determine the pH for the best location to plant. For further information on soil testing, refer to the fact sheet HGIC 1652, Soil Testing. It is not recommended to plant boxwood alongside plants that prefer acidic soil, such as azaleas, camellias, and gardenias, since their soil pH needs differ.

Drainage: Never plant boxwood near downspouts or in any area that stays wet. They require well-drained soil.

Planting Depth: When planting, ensure the top 1/8 of the root ball is above the existing soil level. Deep planting will usually cause loss of plant vigor and sometimes plant death. Boxwood are shallow-rooted plants. Their roots grow in the top 15 inches of soil and spread far beyond the shrub’s drip line.

Watering: Thorough watering encourages the development of a healthy root system. Properly watered plants will be more firmly anchored in the soil and less susceptible to drought and nutritional stress.

Established boxwood should be watered thoroughly weekly if rainfall is less than an inch per week. In the winter, boxwood should be well watered before extreme cold spells. Broadleaved plants, such as boxwood, lose water through their leaves during winter, and some cultivars can take on a bronze color. For more information on boxwood bronzing, see Boxwood Bronzing Blues.

Mulching: To maintain vigorous plants, add 2 to 3 inches of organic mulch over the soil surface yearly. Mulching keeps the shallow roots cool and conserves water by minimizing moisture evaporation from the soil. Mulch also reduces weed problems. Most importantly, mulch reduces the likelihood of the plants getting boxwood blight and other fungal diseases. Remove the mulch from the previous year before adding a new two-inch layer of mulch.

Fertilizing: Boxwood do not need to be fertilized on an annual basis. Have the soil tested to determine if they require fertilization. When a soil test confirms that boxwood do require fertilization, do so in the early spring. Do not fertilize in summer or fall.

Broadcast fertilizer around the base of the plant, just beyond the drip line, on top of the mulch. Fertilizer particles that come into direct contact with the roots of boxwood that have not been mulched can cause root burn. If fertilizer is over-applied, it will cause the leaves to turn brown and may result in dead branches.

If symptoms of nitrogen deficiency begin to appear, it may be time to fertilize. The earliest symptom of nitrogen deficiency is the yellowing of lower leaves. It will have a relatively uniform yellowing that is more pronounced on the older leaves inside the plant. The leaves then become smaller and thinner and turn bronze in the winter. Boxwood leaves will typically stay on the plant for three years. If they fall off earlier, this may be a symptom of nitrogen deficiency.

Pruning: Slow-growing, evergreen shrubs, such as boxwood, have most of their growth from buds near the ends of the branches. Some develop a dense outer shell of foliage with only a few leaves in the center. Thinning is a type of pruning that reduces the number of branches at the outer edge of the shrub. Preferably, thinning should be done annually. Thinning can be done any time when the temperature is above freezing. Thinning is the most important maintenance activity for keeping English boxwood (B. sempervirens ‘Suffruticosa’) healthy. Without adequate light or air circulation, the interior leaves die, with few leaves on the ends of the branches. Thinning will allow the center of the plant to receive sun and air. Much of the poor health of boxwood is a result of not thinning the plant. Very thick foliage encourages fungal leaf spot diseases and twig blight.

Boxwood may be sheared to encourage additional branch development and to maintain a desired shape. The best time to shear the plants is in early June. Do not shear boxwood in late summer or after mid-August since this may force new growth, which will not have sufficient time to harden off before frost.

To restore overgrown boxwood or control their growth, they need to be cut back which is best done in late winter or early spring before new growth emerges. If a small amount is to be cut, the entire pruning can be done at one time. A two-step approach is best if more severe pruning is needed. First, cut large branches on just one side of the plant. In the second year, the other half of the plant would be pruned similarly.

Problems

Boxwood are susceptible to many diseases. Since 2023, boxwood dieback, a fungal disease, has increased in southern states, including South Carolina. Since 2011, boxwood blight has become a concern when it reached the United States from Europe. It was discovered in South Carolina in 2016. Other diseases affecting boxwood include boxwood decline, foliage and twig blights, and Phytophthora root rot.

Insects that affect boxwood include boxwood moth, boxwood leafminer, boxwood psyllid, nematodes, and boxwood mite. More information on these problems may be obtained from HGIC 2052, Boxwood Diseases & Insect Pests.

Species and Cultivars

Listed below are the most commonly available species of boxwood and a sample of their cultivars:

Littleleaf boxwood (Buxus microphylla) is native to Japan. It has the smallest and densest leaves of all the boxwood and a slow growth rate. It can be shaped into topiary, hedges, and bonsai. It is cold hardy in USDA planting zones 6 to 9 and is the most heat-tolerant boxwood. It is highly resistant to boxwood blight.

‘Compacta’ (B. microphylla ‘Compacta’) is the smallest and slowest growing of the boxwood, reaching 8 to 10 inches tall in 15 years. It is often used for bonsai and is sometimes labeled as ‘Kingsville Dwarf’.

‘John Baldwin’ (B. microphylla ‘John Baldwin’) is a tall shrub that can be trained into a formal shape, most often into a conical form. It grows 3 to 4 feet tall by 2 to 3 feet wide with a medium growth rate of up to 3 inches annually. Its leaves have a bluish cast.

‘Little Missy’ (B. microphylla ‘Little Missy’ PP 24,703) is a compact rounded shrub reaching 2 ft high by 2 ft wide. It needs very little pruning because of its slow growth rate. It is cold hardy to USDA planting zones 5. This cultivar is also known as ‘Cole’s Dwarf.’

Baby Gem™ boxwood ((B. microphylla ‘Gregem’ PP21159) has bright green rounded leaves.
Barbara H. Smith, © 2023 HGIC, Clemson Extension

Japanese boxwood (Buxus microphylla var. japonica) is a larger plant than the species, reaching six or more feet tall and wide. However, many cultivars are shorter. Use it for foundation plantings, formal hedges, or as a specimen plant. It is cold hardy in USDA planting zones 6 to 9 and is highly resistant to boxwood blight and nematodes. It is susceptible to boxwood mites and leafminers.

‘Baby Gem™’ (B. microphylla ‘Gregem’ PP21159) is a medium-rounded shrub reaching 4 feet tall and 4 feet wide, although it is mostly seen pruned to a smaller size of 2 or 3 feet tall. It has very small and dense leaves and can be pruned into a low wall-type hedge to delineate parts of a garden. It can be used in foundation plantings, to edge a sidewalk, or as a specimen in the garden or containers.

‘Green Beauty’ (B. microphylla var. japonica ‘Green Beauty’) is a mid-sized cultivar with a rounded habit. It reaches 3 to 5 feet tall by 3 to 5 feet wide and is slightly wider than tall. It can be grown as a foundation plant or trained into formal shapes and hedges.

‘Unraveled’ (B. microphylla var. japonica ‘Unraveled’) is a weeping shrub that can be trained to a height of 4 feet with a weeping spread of 7 feet.

‘Winter Gem’ (B. microphylla var. japonica ‘Winter Gem’) has a rounded habit and reaches 4 feet tall and wide. It has a fast growth rate. In spring, its new foliage emerges as a bright lime green color, then turns dark green as it matures. Sprinter® (B. microphylla ‘Bulthouse’ PP25,896) is considered an improved form of ‘Winter Gem.’

American or common boxwood (Buxus sempervirens) is not native to the United States despite its name. It is native to Europe, parts of western Asia, and northern Africa. The species can

Variegated English boxwood (B. sempervirens ‘Variegata’) has dark green leaves with white margins.
Barbara H. Smith, © 2022 HGIC, Clemson Extension

grow to a height of 15 feet or more, but most cultivars are considerably smaller. It is cold hardy in USDA planting zones 5 to 8 and benefits from shade, especially afternoon shade. This species is the least resistant to Boxwood blight. It is resistant to root-knot and other nematodes.

‘Arborescens’ (B. sempervirens ‘Arborescens’) is commonly called tree boxwood because it can reach a height of 15 feet and a width of 10 feet. It can be shaped into large topiary forms or hedges.

‘Dee Runk’ (B. sempervirens ‘Dee Runk’) is a tall cultivar with a conical form. It reaches 8 to 10 feet tall and 2 to 3 feet wide and has a medium growth rate. It is often grown as a tall hedge, a specimen for a narrow space, or as a tall accent at the end of a foundation planting.

‘Suffruticosa’ (B. sempervirens ‘Suffruticosa’) is commonly known as English boxwood and is one of the most widely grown cultivars. It is a slow-growing dwarf shrub most often grown as a low hedge and used in formal garden design. It is known for the odor of its foliage. It is very susceptible to boxwood blight, mites, and psyllids.

‘Variegata’ (B. sempervirens ‘Variegata’) is a variegated English boxwood with white to cream margins on its leaves. It reaches 3 to 5 feet tall and 3 to 4 feet wide and has a slow growth rate. It is often grown as a specimen or container plant.

Korean boxwood (Buxus sinica var. insularis) is native to Asia. It has a more open habit than other boxwood, and its foliage is less dense. Its leaves are a lighter green and prone to turning bronze in the winter. It is more sun tolerant than other species. It is the most cold hardy boxwood and can be planted in USDA planting zones 4 to 9. It is highly resistant to boxwood blight and leafminers.

‘Nana’ (B. sinica var. insularis ‘Nana’) is a low-spreading shrub that grows less than 2 feet tall, with a spread of up to 4 feet wide. It is grown as edging, foundation planting, and as small specimens. Another name for this plant is ‘Franklin’s Gem’.

‘Wintergreen’ (B. sinica var. insularis ‘Wintergreen’) is a medium-sized, fast-growing shrub. It can be maintained at 4 ft tall, grows 4 to 6 inches annually, and is mostly used for hedging. This cultivar is less prone to turn bronze in the winter and is highly resistant to boxwood blight.

Hybrids: In today’s world of boxwood breeding, many crosses create hybrids with the best traits of both parents. These hybrids typically have the most disease resistance.

BetterBoxwood® hybrids are the result of European breeding and trialing over the course of twenty years. These hybrids were bred to be boxwood blight-resistant. They are cold hardy in USDA planting zones 5 to 9.

Heritage™ (B. x ‘HER2010B02’) is a taller-than-wide shrub reaching 3 to 4 feet tall by 2 to 3 feet wide. Its dark green foliage resembles American boxwood and is used as a hedge or foundation planting.

Renaissance™ (B. x ‘HER2009B01’) is a wider-than-tall cultivar reaching 3 feet tall by 4 to 5 feet wide. Its foliage is light green. It can be grown as a groundcover type shrub.

NewGen® boxwood hybrids result from breeding for resistance to boxwood leafminer, boxwood blight, and other diseases. These plants were trialed for landscape performance in locations across the United States and are cold-hardy in USDA planting zones 5 to 8.

Freedom® (B. x ‘SB 300’ PP32421) is a rounded habit shrub slightly taller than wide, reaching 3.5 feet tall and wide. It has a fast growth rate and uniform habit, which lends it to formal gardens or hedges.

Independence® (B. x ‘SB108’ PP28888) has a rounded habit and reaches 3 feet tall and wide. It grows at a moderate rate. Its medium size lends it to edging and foundation planting. It has deep green foliage.

‘Green Velvet’ boxwood ((B. ‘Green Velvet) has dark green leaves that rarely turn bronze in the winter.
Barbara H. Smith, © 2022 HGIC, Clemson University

Liberty Belle™ (B. sinica var. insularis ‘RLH-BI’ PP 24,443) is a low-growing, wider- than- tall shrub that reaches 1.5 feet tall by 3 feet wide. It is a very slow grower and was bred and trialed in South Carolina.

Sheridan Nursery in Canada released Korean and English boxwood crosses in the 1970s. These hybrids are cold hardy and compact like the Korean boxwood and have deep green foliage like the English boxwood. They are moderately resistant to boxwood blight. They are cold hardy in USDA planting zones 5 to 8.

‘Green Gem’ (Buxus ‘Green Velvet’) is a dwarf-rounded shrub for containers and edging reaching 2 feet tall and wide.

‘Green Mound’ (Buxus ‘Green Mound’) is a rounded shrub reaching 2 to 3 feet tall and wide.

‘Green Mountain’ (Buxus ‘Green Mountain’) is naturally cone-shaped and is often used for topiary. It is also used for a hedge reaching 5 feet tall by 3 feet wide.

‘Green Velvet’ (Buxus ‘Green Velvet’) is the most popular of these hybrids, reaching 3 feet tall by 4 feet wide and has the darkest green foliage of all the Sheridan boxwood crosses. The foliage rarely turns bronze in winter.

Originally published 12/98