Arborvitae are a popular and effective choice for creating year-round privacy screens. Their dense, evergreen foliage provides an immediate visual barrier, making them a favorite for planting along boundaries. The long-term success of this living fence depends on correct initial spacing from any structure, particularly a fence. Determining the proper planting distance ensures the plant’s health, prevents damage to the structure, and minimizes future maintenance efforts.
Understanding Arborvitae Mature Width
The distance an arborvitae should be planted from a fence depends entirely on the specific cultivar’s mature width. Different varieties have vastly different growth habits, ranging from narrow columns to broad pyramids. Failing to account for this mature size is the most common planting mistake, leading to significant problems later.
For example, the popular ‘Emerald Green’ arborvitae (Thuja occidentalis) matures to a width of only 3 to 5 feet. In contrast, the fast-growing ‘Green Giant’ arborvitae (Thuja plicata x standishii) often reaches a mature spread of 12 to 20 feet. Always check the plant tag or nursery information for the ultimate mature width before planting.
Calculating the Minimum Planting Distance
The fundamental rule for planting distance is to ensure the mature width of the tree does not fully encroach upon the fence or structure. Plant the tree’s trunk at a distance equal to half of its expected mature width. This calculation ensures the center of the plant is positioned to allow its full spread without pushing against the boundary.
A ‘Green Giant’ arborvitae with a 12-foot mature width requires a minimum distance of six feet from the fence line. It is recommended to add an extra buffer of 1 to 2 feet beyond this half-width measurement. This additional space allows for maintenance access and promotes healthy air circulation around the foliage. Therefore, a ‘Green Giant’ should be planted 7 to 8 feet from the fence, while a narrower ‘Emerald Green’ (5-foot mature width) requires 3 to 4 feet.
Health and Maintenance Implications of Tight Spacing
Planting an arborvitae too close to a fence compromises its health and increases maintenance burdens. When foliage grows directly against a solid structure, the lack of airflow traps moisture and humidity. This stagnant environment is conducive to the proliferation of fungal pathogens, such as blight and canker diseases.
The side of the arborvitae facing the fence will also be deprived of sunlight, causing the foliage to thin out and die back. This results in a one-sided plant with a brown patch against the fence, negating its purpose as a screen. Over time, the expanding trunk of a large cultivar can exert pressure on a wooden fence, potentially warping or damaging the structure. The buffer space ensures room to access and prune the fence-side of the tree to maintain its shape and health.
Property Lines and Neighbor Considerations
The physical location of a fence does not always align with the property line, which is an important distinction when planting near a boundary. Before planting, consult your property survey to confirm the location of the property line. Some local municipalities enforce specific setback requirements, dictating the minimum distance from the property line that any structure or large plant must be located.
Planting large, fast-growing evergreens near a shared boundary requires consideration for neighbor relations. Roots from mature arborvitae, while not typically invasive, can still cause concern or minor damage over decades. Discussing your planting plan with your neighbors beforehand can prevent future disputes regarding encroaching branches or leaf litter. Adhering to the “half mature width plus buffer” rule helps ensure that your plants remain contained within your property’s space.