Boxwood shrubs (Buxus) are popular, dense evergreen plants often used in landscaping to create formal borders and hedges. Determining the correct number of boxwoods relies directly on the plant’s mature size and the desired aesthetic. Calculating the right quantity is necessary for achieving a uniform, dense result, whether planning a short border or an extensive boundary hedge. Over- or under-planting can lead to an unhealthy, uneven hedge or significant future replacement costs.
Choosing the Right Boxwood Variety for Your Goal
The first step in any calculation is selecting a boxwood variety whose mature size aligns with the project’s long-term goal. Different cultivars possess dramatically different mature spreads, directly influencing the required planting distance. For instance, if the goal is a low, neat edge for a walkway, a dwarf variety is the appropriate choice.
A popular, moderately sized cultivar like ‘Winter Gem’ typically matures to a spread of about 3 to 4 feet, making it suitable for medium-height hedges. For a taller, more substantial screen, a variety like ‘Faulkner’ may be better, reaching a mature height of 4 feet with a 3-foot spread. Conversely, if the intent is a very compact, low border, a cultivar like ‘Green Velvet’ is a common choice. Always check the plant tag or nursery information for the plant’s mature width before beginning any mathematical layout.
Calculating Plant Density for Hedges and Mass Plantings
The calculation for a linear hedge is based on the total length of the area and the desired spacing between the plants. To create a dense, continuous hedge where the plants merge to form a solid green wall, space them at approximately two-thirds (2/3) of the plant’s mature width. For example, if a variety is expected to mature to a 3-foot width, the ideal spacing for a dense hedge would be 2 feet (3 feet multiplied by 0.66).
The formula for a straight run is: Total Linear Feet / Spacing Distance = Number of Plants. If the project is a 50-foot hedge using 2-foot spacing, the calculation is 50 feet / 2 feet, equaling 25 plants. For a looser border where individual plant shapes are still visible, the spacing can be set closer to the plant’s full mature width.
Mass plantings, such as filling a large rectangular bed, require calculating the total square footage. The total area is divided by the area a single mature plant will occupy, based on the desired spacing. If the plants are spaced 3 feet apart, the area covered by one plant is 9 square feet (3 feet x 3 feet). The formula, Total Square Footage / Individual Plant Area, provides a base estimate for the number of plants needed.
Adjusting the Count for Corners, Curves, and Foundation Layouts
Straight-line calculations must be modified when the planting involves changes in direction or proximity to structures. Corners require specific adjustment to ensure the hedge remains dense and visually continuous at the apex. A common technique is to slightly overlap the spacing at the corner, placing the plants closer than the standard spacing.
For a 90-degree corner, the two plants meeting at the turn should be centered at the intersection point, which naturally reduces the distance between them and the adjacent plants. Curves also demand tighter spacing than straight sections, especially for smaller radii, to prevent visible gaps from forming. Tighter curves may require reducing the standard spacing by 10% to 20%.
Foundation plantings, where boxwoods are placed against a building, require consideration of the mature width to prevent crowding. Plants should be set back from the wall by at least half their mature spread to allow for airflow and growth, which prevents disease and structural damage. This setback may reduce the total number of plants needed compared to a simple hedge running parallel to the foundation.