Boxwood shrubs (Buxus) are popular evergreen plants used in landscape design, prized for their dense foliage and ability to be shaped into formal hedges, borders, and topiaries. Their compact nature and year-round green color make them staples for foundation plantings and defining garden spaces. A key consideration for gardeners choosing this species is the speed at which it grows, as this determines the maintenance effort required. The question of whether boxwoods grow fast is nuanced, as their growth rate is generally slow when compared to many other common landscape shrubs.
Defining Boxwood Growth Rates
Most boxwoods fall into the slow to moderate growth rate categories, which is why they are often used for precise, manicured shapes. A slow growth rate is defined as adding less than 3 inches of new growth per year, while a moderate rate adds between 3 and 6 inches annually. Dwarf cultivars, such as the English Boxwood (Buxus sempervirens ‘Suffruticosa’), may only gain 1 to 2 inches of height each year. Even the varieties considered “fast-growing” for a boxwood rarely exceed an annual increase of 6 inches, which is still quite slow compared to other ornamental shrubs. This naturally slow pace means that once a boxwood reaches its desired size, it requires less frequent pruning to maintain its form.
Environmental Factors Influencing Growth Speed
A boxwood’s genetic makeup sets its potential growth speed, but environmental conditions determine if it reaches the high or low end of that range. Optimal soil conditions are paramount, as boxwoods are highly susceptible to root rot, necessitating well-drained soil. They are shallow-rooted plants, meaning they cannot tolerate sitting in continuously wet ground. The ideal soil pH for boxwood health is neutral to slightly alkaline, generally ranging between 6.8 and 7.5.
Sunlight exposure also plays a part in the shrub’s performance. Boxwoods perform best in locations that receive partial or dappled shade, needing protection from intense afternoon sun. Too much exposure can lead to winter damage, commonly referred to as bronzing. Consistent moisture is necessary, but overwatering is a common cause of decline. Fertilization should be light and applied in late fall or early spring to support the root system without encouraging tender new growth susceptible to early frost.
Comparing Common Boxwood Varieties
The growth potential of a boxwood is largely determined by the specific species or cultivar chosen. The classic English Boxwood (Buxus sempervirens ‘Suffruticosa’) is famous for its extremely slow growth, making it a preferred choice for small, formal edging. In contrast, the American Boxwood (Buxus sempervirens) is a faster-growing type that can eventually reach the size of a small tree if left unpruned.
Certain Korean Boxwood cultivars, such as ‘Winter Gem’ or ‘Wintergreen’, are frequently cited for their comparatively faster growth, often adding 4 to 6 inches each year. The ‘Green Mountain’ hybrid is another medium-to-fast growing variety, capable of adding 3 to 6 inches annually, making it a popular choice for taller hedges. Selecting the right cultivar is the most direct way to manage expectations regarding growth, as a genetically slow-growing plant will never achieve the rate of a naturally faster variety.
Managing Size Through Pruning
Pruning is the primary method for managing boxwood size and shape, and these shrubs tolerate heavy cutting well. The best time for major pruning is in late winter or early spring, just before the new growth flush begins. This timing allows the plant to quickly cover the cut areas with fresh foliage. Pruning techniques fall into two categories: shearing and thinning.
Shearing
Shearing involves clipping the outer layer of foliage to maintain a dense, formal shape like a hedge or topiary.
Thinning
Thinning involves selectively cutting back inner branches to the main stem to allow better light penetration and air circulation throughout the shrub. This internal thinning is crucial for maintaining a healthy plant and preventing the dead, brown interior often seen in heavily sheared boxwoods. Gardeners attempting to reduce the size of an overgrown boxwood should do so gradually, removing no more than one-third of the total foliage in a single season.