Boxwood shrubs are popular evergreen plants in landscaping, valued for their dense foliage and year-round structure. They are frequently used for creating formal hedges, parterre gardens, and defined borders. The mature size of a boxwood depends entirely on the specific species and cultivar selected. Hundreds of varieties exist, ranging from tiny groundcovers to large, upright shrubs.
Categorizing Boxwood Mature Sizes
The final height is the boxwood’s most distinguishing characteristic. Cultivars are generally grouped into three size classes when fully mature under favorable conditions. These sizes reflect the plant’s potential height after approximately 15 years of growth, though some varieties take longer to reach their ultimate dimensions.
Dwarf Varieties
Dwarf boxwoods are ideal for low edging, knot gardens, and small spaces, as their mature height rarely exceeds three feet. The classic ‘Morris Midget’ (Buxus microphylla) is an extremely slow grower, typically reaching only 12 to 18 inches tall and wide. The traditional English Boxwood (Buxus sempervirens var. suffruticosa) is prized for its compact, rounded habit, generally maturing to a height of two to three feet. These small dimensions are perfect for defining pathways or planting beneath windows.
Medium Varieties
The medium category includes the most common hedge-forming boxwoods, maturing to heights between four and six feet. Cultivars like ‘Green Velvet’ and ‘Green Mountain’ are popular choices, often reaching a dense, rounded size of three to five feet tall and wide. These varieties are frequently used for creating medium-height privacy screens and structural garden divisions. The ‘Green Beauty’ boxwood commonly grows four to six feet tall, making it a reliable choice for foundation plantings.
Large/Tree-Form Varieties
Some boxwood species can become very large specimens if left untrimmed. The American Boxwood (Buxus sempervirens) is known for its upright habit and can reach mature heights of five to ten feet, with some old specimens exceeding twelve feet. These larger varieties are excellent for creating tall, dense privacy hedges or standalone, tree-like accents. The columnar ‘Graham Blandy’ cultivar is a tall, narrow variety that can reach 15 feet while remaining only two to four feet wide, making it useful for narrow screening.
Understanding Growth Rate and Time to Maturity
The time required to reach mature size is crucial, as boxwoods are universally characterized by their slow growth rate. Most cultivars add a modest three to six inches of new growth per year, depending on the variety and growing conditions. Dwarf types, such as ‘Morris Dwarf’, can be exceptionally slow, sometimes growing less than one inch annually.
Because of this gradual growth, boxwoods take a significant amount of time to reach their full potential size. Moderate-sized varieties may require 10 to 15 years to fully mature. Larger varieties, like the American Boxwood, can take 20 years or more to reach their maximum height. Environmental factors such as soil quality, adequate watering, and sun exposure directly influence this rate, with optimal conditions encouraging slightly faster growth.
Maintaining Desired Height and Shape
Knowing a boxwood’s mature height allows for informed pruning. Pruning is essential for maintaining a specific, desired height. The best time for major pruning is typically in late winter or early spring, just before the plant begins its new flush of growth.
Size Reduction
For size reduction, renewal pruning involves making cuts deep into the shrub’s interior, which encourages new growth from the stem. When reducing the overall size of an overgrown boxwood, it is recommended never to remove more than one-third of the plant’s mass in a single season to prevent shock. This reduction may need to be phased over two or three years for severely overgrown shrubs.
Shape Maintenance
Light shearing, often performed later in the spring or mid-summer, is used to maintain a formal, manicured shape. This involves removing only the bright green new growth to keep the hedge crisp.