The common boxwood (Buxus sempervirens) is a popular evergreen shrub widely used in landscaping due to its dense foliage and adaptability. Understanding its growth rate is important for garden planning, proper care, and selecting the right variety for your landscape.
Understanding Common Boxwood Growth
Common boxwood’s growth rate refers to its average annual increase in height and width. Generally considered a slow-growing shrub, most varieties grow approximately 3 to 6 inches per year, contributing to their dense, compact form and suitability for formal hedging and topiary. Dwarf varieties may grow even slower, sometimes adding only 0.5 to 1 inch annually. This slow growth means boxwood maintains its shape well, requiring less frequent pruning compared to faster-growing shrubs.
Factors Influencing Growth
Several environmental and cultural factors significantly influence the growth rate of common boxwood. Light exposure is a primary factor. Boxwoods prefer partial or dappled shade, receiving 4 to 6 hours of direct sunlight daily. While they tolerate full sun, excessive exposure can cause leaf scorch or winter bronzing. In full shade, growth slows, and foliage may appear less vibrant.
Well-draining soil is crucial to prevent root rot. Boxwoods thrive in loamy soil that balances drainage and moisture retention. The ideal soil pH ranges from 6.5 to 7.5 (slightly acidic to neutral).
Watering practices also impact growth. Young plants need consistent moisture, with deep weekly watering for two years. Established boxwoods are moderately drought-tolerant but benefit from regular deep watering during dry spells. Overwatering or poorly draining soil can cause root issues.
Proper fertilization promotes healthy growth, but over-fertilization, especially with nitrogen, is not recommended. A slow-release granular fertilizer applied in spring is beneficial. Climate and hardiness zones also influence growth; extreme temperatures or unsuitable zones (typically USDA zones 5-8) can stress the plant, causing slower growth or winter damage.
Managing Boxwood Growth
Managing common boxwood growth involves practical techniques that work with its natural slow-growing habit to achieve desired landscape effects. Pruning is a key management tool, and due to its slow growth, common boxwood typically requires light, regular trimming to maintain its shape rather than drastic cuts. The best time for pruning is in late winter to early spring before new growth emerges, or in late spring after the first flush of growth for a more formal shape. Avoid heavy pruning in late summer or early fall, as this can stimulate new growth that may not harden off before winter, making it susceptible to cold damage.
Proper spacing during planting is important for both individual specimens and hedges. For hedges, plants are often spaced at half their mature width, ensuring they grow together to form a dense, continuous screen. For example, plants intended for a low hedge might be spaced 12 to 18 inches apart, while larger varieties for a taller hedge could be 3 to 4 feet apart. This spacing allows for adequate air circulation, which is beneficial for plant health and helps prevent disease.
Routine care also supports consistent, healthy growth for boxwoods. This includes applying a 2 to 3-inch layer of mulch around the base of the plant to help retain soil moisture, regulate soil temperature, and suppress weeds. Monitoring for pests and diseases and addressing them promptly helps the plant direct its energy towards growth rather than recovery. Consistent watering, especially during dry periods, ensures the plant remains hydrated, supporting its overall vitality even with its slow growth rate.