Boxwood shrubs (Buxus species) are prized for their dense, evergreen foliage and their ability to be shaped into formal hedges or left as natural specimens. These slow-growing plants offer year-round structure for borders and foundation plantings. However, the long-term health and aesthetic outcome of a boxwood planting rests almost entirely on correct initial spacing. Determining the right distance is a calculation that ensures the shrubs have the necessary room to mature and thrive.
Factors That Determine Boxwood Spacing
The distance required between boxwood plants is determined by two main horticultural variables that must be considered before planting begins. The mature size of the specific cultivar is the most important factor. Boxwoods range significantly, from dwarf varieties that may only reach two to three feet wide to larger American Boxwood types that can eventually spread up to 20 feet. Checking the plant tag or nursery information for the ultimate mature width is the single most important step in the spacing process.
The second variable is the intended purpose for the shrubs, which dictates whether the plants should eventually touch or remain as distinct individuals. If the goal is a dense, formal hedge, the plants must be spaced much closer than if they are meant to be standalone accent shrubs. A hedge requires the plants to grow into each other to form a solid green wall, while a specimen planting showcases the plant’s natural shape. Ignoring these factors leads to either premature crowding or perpetual gaps in the landscape.
Specific Spacing Guidelines for Different Uses
For creating a dense, interwoven formal hedge, the general planting rule is to space the plants at a distance equal to half of their expected mature width. For example, a dwarf cultivar like ‘Green Gem’ that matures to a four-foot spread should be planted with the center of each plant two feet apart. This close spacing ensures the branches meet and interlock relatively quickly, forming a solid, continuous barrier. For larger varieties, such as a tall American Boxwood hedge, this calculation may mean planting the shrubs three to four feet apart to allow for proper density without excessive crowding.
When planting boxwoods as individual specimen shrubs, the spacing should be equal to or slightly greater than the plant’s full mature width. A cultivar expected to reach five feet wide should be planted at least five feet away from any neighboring plant or structure. This allows the shrub to develop its natural, often globe or pyramidal, shape without being compressed. This wider spacing promotes better light penetration and air circulation, which contributes to overall plant vigor.
For foundation planting, boxwoods should be positioned far enough away from the structure to prevent future contact. A distance of 18 to 24 inches from the wall is advised, regardless of the ultimate mature width of the shrub, to ensure air can circulate completely around the plant. This practice prevents moisture and humidity from building up against the foundation and the shrub’s interior, which can lead to health issues. Planting too close can also inhibit routine maintenance and pruning as the shrub matures.
Consequences of Improper Spacing
Planting boxwoods too closely together is a common mistake that creates conditions favorable for fungal diseases. Overcrowding significantly reduces air circulation around and within the dense foliage canopy. This lack of airflow traps moisture and humidity, creating a damp environment where pathogens, particularly the fungus responsible for Boxwood Blight (Calonectria pseudonaviculata), can thrive and spread rapidly.
Crowding inhibits sunlight from reaching the lower and inner branches of the shrub. Over time, these shaded parts will defoliate, leaving the plant with an unattractive, thin interior and a hollow appearance. This necessitates more aggressive and frequent pruning to maintain a desirable shape, which stresses the plant.
Conversely, planting too far apart means the shrubs will take many years to grow into each other, failing to achieve the desired continuous look. While this error does not pose the same immediate health risks as crowding, it results in a landscape that appears gapped and unfinished for far longer than necessary. Proper spacing balances the need for immediate aesthetic appeal with the long-term biological requirements of the boxwood.