If you're looking for an evergreen shrub that's tough, versatile and easy to grow, the boxwood (Buxus spp.) may be the right choice for you. Available in different shapes and sizes, depending on the species and cultivar, boxwoods can fit well in many different garden areas. Generally frost-tolerant shrubs, boxwood varieties vary slightly in their preferred climate.
The boxwood plant has been cultivated for thousands of years, from the time of the ancient Greeks and Romans. About 90 species of boxwoods exist, but only three species are widely grown: littleleaf boxwood (Buxus microphylla), which grows in U.S. Department of Agriculture plant hardiness zones 5 through 8 or 9; Korean boxwood (Buxus sinica var. insularis), which grows in USDA zones 4 through 8; and American or common boxwood (Buxus sempervirens), which grows in USDA zones 5 or 6 through 8. The various cultivars and subspecies may have slightly different hardiness than the species.
All boxwoods are evergreens with oval green leaves about 1/2 to 1 inch long. They have a generally upright, oval to rounded growth habit and usually grow as multistemmed shrubs, although some varieties can be pruned into a more treelike shape. Boxwoods vary greatly in size, from 1 to 2 feet tall to 15 feet tall. When given the right conditions, boxwoods branch extensively and become extremely dense, with many small branches and profuse foliage that obscure the interior of the plant. Generally slow-growing plants, they have a naturally pleasing form and don't need pruning, but they also respond well to shearing of the outer parts of the plant and fit well into either a formal or informal garden.
Boxwood grows in either full sun or partial shade, but performs best in a spot that gets some shade, especially in the afternoon in areas with hot summer sun. In regions with cold winters, some shade also helps prevent desiccation of the plant's leaves in cold winds or when the ground is frozen and the plant can't take up water. It does best in moist, loamy soil, but adapts to any type of well-draining soil. If your soil is rich in clay and drains poorly, adding sand at planting can improve its drainage. Mulching the plant helps it grow well by conserving soil moisture; the mulched area should extend at least 3 feet from the plant's base to keep down competition for water from grass and other plants.
Among the many boxwood cultivars available for planting, several are especially useful. The American boxwood variety "Dee Runk" (Buxus sempervirens "Dee Runk") has an upright, narrow form and reaches a height of about 8 feet in 15 years. The cultivar called "Fastigiata" (Buxus semperiverens "Fastigiata") is broader but similar-sized, while "Jensen" (Buxus semperiverens "Jensen") is naturally round and only about 2 feet tall. These three boxwoods grow in USDA zones 6 through 8. Among littleleaf boxwoods, "Green Pillow" (Buxus microphylla "Green Pillow") is low and mounding, about 1 foot tall and 2 feet wide after 15 years, and grows in USDA zones 5 through 8. Korean boxwood "Wintergreen" (Buxus sinica var. insularis "Wintergreen") is about 4 feet tall and equally wide after 15 years, while "Nana" (Buxus sinica var. insularis "Nana") is only 1 1/2 feet tall but 3 feet wide at an equal age.