Boxwood is a genus of about 70 species of flowering shrubs that are commonly grown as small, compact bushes or hedges. The name boxwood originates from the plant's easy to maintain box-like appearance. However, the plant exhibits a sprawling behavior in the wild. Most varieties have unattractive flowers and are grown as privacy hedges or borders. The four primary types of boxwood plants are English, American, Korean and Japanese boxwood.
English boxwood, B. sempervirens 'Suffruticosa,' is the most commonly grown cultivar, and it was first cultivated in the early 1700's in the United States. It can reach 3 feet in height and usually grows about 1 inch per year. English boxwood is rounded, and the overall shape of the plant is similar to a cloud. It is considered non-ornamental because the flowers are not visually appealing compared to other plants. English boxwood is an evergreen and blooms during the spring.
American boxwood, also known as common boxwood, is a small tree that grows to 10 feet in height, although some older plants can grow up to 20 feet. American boxwood is an evergreen and is very tolerant of cold weather, making it a good choice for cooler, northern regions. American boxwood blooms during the spring, but produces small, pale green flowers that are commonly overlooked. American boxwood is grown primarily for its foliage, which grows to about 1½ inches in length. The leaves are waxy and dark green in color, with pale undersides.
Korean boxwood is a variety that grows in an open habit, as opposed to the dense foliage common in other species of boxwood. This increases the circulation and the amount of light that reaches the inner portions of the plant, making it more disease resistant. It is winter hardy, but during periods of extremely low temperatures, the leaves may brown. However, in the spring the green will return and the plant will resume growth as usual.
Korean boxwood forms oval-shaped leaves that usually only grow to about ½ inch in length. The flowers are small, unattractive and green or yellow in color. Korean boxwood grows to about 4 feet in height and blooms during spring. It is hardy in zones 4 through 9.
Japanese boxwood was first grown in the United States in 1890 and is considered one of the most adaptable species of boxwood available. It can grow up to 8 feet in height with a spread of about 6 feet if grown in the proper environment. The foliage is dark green and grows to about 1 inch in length. It is evergreen, though in cooler climates the leaves may adopt a yellow or brown tinge. Japanese boxwood is commonly grown as a low hedge; it forms an excellent border when maintained. The flowers bloom in April, but are not showy. Additional blooming is usually discouraged by removing spent flowers.