HARDINESS: Zones 5 to 8
PREFERRED SOIL pH: Neutral to slightly acid
PREFERRED SOIL TYPE: Fertile, well-drained
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Slow-growing evergreens with small leaves; for beds, edging, hedges
SEASON OF INTEREST: Year-round
FAVORITES: 'Myrtifolia', 'Vardar Valley', 'Curly Locks', 'Green Gem'
QUIRKS: Shallow roots are easily injured by cultivation
GOOD NEIGHBORS: English ivy, liriope, magic lily, rose, tulip
WHERE IT GROWS BEST: In fertile, well-drained soil where winters are not severe
POTENTIAL PROBLEMS: Scale; root rot
PRUNING: Prune or shear any time from late winter to early summer
CRITTER RESISTANCE: Good
SOURCE: Nursery plants
DIMENSIONS: 1-12 ft (0.3-3.7 m) tall, 1-4 ft (0.3-1.2 m) wide; leaves to 1 in (2.5 cm)
Boxwood in the Landscape
Boxwood is a widely grown evergreen that deserves its popularity. Dwarf forms can be used to anchor flower beds or edge walkways, while larger types fit well into foundation plantings. Boxwoods make an excellent backdrop for bulbs or perennials with light foliage and add a background for sitting areas or entryways. Be careful when digging around boxwood roots. Injured roots are entry points for soil-borne, fungal root-rot diseases.
Typically slow-growing, boxwood will endure for centuries. Its only limitation is poor tolerance of extreme cold. While there are cultivars suited to every area, common boxwood (Buxus sempenirens) is usually hardy to Zone 5, while littleleaf boxwood (B. microphylla) is hardy to Zone 6 and tolerates summer heat better.
Boxwoods Old and New
Cultivars of common boxwood offer many variations in size and shape. 'Myrtifolia', grown since the 1700s, is a 4 ft (1.2) shrub with narrow leaves. The dark green 'Handworthensis', grown since the 1870s, is strongly upright, as is 'Graham Blandy', which becomes a column reaching 12 ft (3.7 m) tall. 'Vardar Valley', a relative newcomer from the 1950s, takes cold in stride and forms a mounding shape to 2 ft (0.6 m) high and 3-4 ft (1-1.2 m) wide. Often called edging box, 'Suffruticosa' is another old variety that seldom grows taller than 2 ft (0.6 m), making it good for a low hedge.
Littleleaf boxwood is generally smaller in leaf and stature than common boxwood. 'Green Pillow' has a spreading habit, reaching only 15 in (38 cm) tall but 3 ft (1 m) wide. 'Curly Locks' is an upright grower, to 2 ft (0.6 m), with slightly twisted branches. A very slow-growing variety known as Korean boxwood (B. m. var. koreana) tolerates both heat and cold well but may still brown in winter. 'Green Mountain' and 'Green Gem' overcome this defect, remaining green all winter and reaching 2—3 ft (0.6— 1 m) tall and wide.
Prepare planting holes by working in a 4 in (10.2 cm) deep layer of compost or other organic matter, as well as sharp sand if the site catches runoff water. Set out plants in either spring or fall and expect to see little new growth the first year. Boxwoods often do not reach full size for 5-8 years.
Boxwoods have a naturally neat look, but you can prune them if you prefer a tight shape. Avoid pruning in late summer. The resulting growth is easily injured by freezing weather.
Most cultivars offer good disease resistance, but boxwood can have problems with scale, tiny immobile
spider relatives that hide on leaf undersides and suck plant juices, causing leaves to turn pale. Control spider mites with a neem-based insecticide used per label directions. When entire plants or major sections turn brown, the problem is likely root rot. Remove plants promptly and replace with a moisture-tolerant species.