Boxwood shrubs (Buxus species) are valued for their dense, evergreen foliage and their ability to be shaped into formal hedges, borders, and topiaries. Although generally slow-growing, their popularity means gardeners often seek varieties that establish themselves quickly. The growth rate is determined by the shrub’s genetic potential, but it is dramatically influenced by care and environmental conditions. Finding the fastest boxwood requires understanding the top-tier cultivars and optimizing their growing environment.
Identifying Rapidly Growing Boxwood Varieties
Boxwoods are classified as slow-growing shrubs, with most varieties adding only two to four inches of new growth annually. The fastest-growing cultivars typically achieve four to six inches of growth per year under ideal conditions. This rate is considered rapid for a boxwood, though slower than many other landscape shrubs.
The cultivars that reliably reach this faster growth rate often belong to the American Boxwood group (Buxus sempervirens). Cultivars like ‘Sprinter’ and ‘Wintergreen’ are noted for their vigorous habits, making them excellent choices for quickly establishing a dense hedge. ‘Sprinter,’ a hybrid of Buxus microphylla, is specifically bred for improved growth.
The ‘Green Mountain’ boxwood also exhibits a moderate to fast growth rate, averaging four to six inches per year and developing an upright, pyramidal shape. Selecting these genetically faster varieties is the first step toward achieving maximum height quickly. However, even the fastest boxwood requires a supportive environment to reach its full potential.
Essential Conditions for Optimal Growth Speed
Maximizing a boxwood’s growth speed depends on providing precise environmental support that encourages continuous, healthy new shoot development. Boxwoods thrive in well-drained soil; poor drainage is a common cause of stunted growth due to root stress. The ideal soil pH is neutral to slightly alkaline, specifically ranging between 6.8 and 7.5, which ensures the plant can efficiently absorb necessary nutrients.
Boxwoods can tolerate partial shade, but planting them in full sun or morning sun with afternoon shade encourages denser and more robust growth. Consistent moisture is paramount, especially during the establishment phase, as their shallow root systems are susceptible to drought stress. A two- to three-inch layer of organic mulch helps keep the soil cool and retain moisture around the roots.
To fuel vigorous new growth, fertilization should be timed strategically. Applying a slow-release, balanced granular fertilizer, such as a 10-10-10 or a nitrogen-heavy 10-6-4 formula, in late fall or early spring promotes both root and foliar development. Late fall fertilization targets root growth during dormancy, while an early spring application supports the strong flush of green growth. Avoid fertilizing in late summer, as this stimulates tender new growth easily damaged by early winter frosts.
Pruning Techniques and Growth Rate
For a boxwood planted to quickly achieve mature height, pruning should be kept to a minimum during the first few years of establishment. Heavy shearing, which involves cutting back a significant portion of the new growth, removes the plant’s upward progress and is best reserved for maintaining a formal shape later. A frequently sheared boxwood will devote energy to recovering lost foliage rather than increasing its overall size.
For rapid height gain, focus on light, selective trimming of only the tips to encourage lateral branching, which contributes to a robust and dense structure. This technique, known as thinning, involves removing select interior branches to allow sunlight and air to penetrate. Improved light and air circulation helps prevent disease and promotes healthy growth from the center of the plant.
The optimal time for any pruning is in late winter or early spring before the new growth begins. This timing minimizes stress and stimulates the strongest possible spring flush, maximizing the growth spurt for the coming season. Minor touch-ups should be done after the first flush of spring growth, but all pruning must cease by mid-summer to ensure new shoots have time to harden off before the first frost.