Arborvitae trees (Thuja) are evergreen conifers known for their dense, upright, conical growth habit. They are frequently used to create privacy screens, windbreaks, and formal garden accents. Determining the correct planting distance is crucial, as it directly influences the trees’ health, their ability to form a solid visual barrier, and future maintenance requirements.
Why Proper Spacing Is Crucial for Plant Health
Planting arborvitae too closely compromises their health and leads to long-term issues. Adequate spacing promotes air circulation around the foliage, which is a primary defense against fungal diseases. When trees are crowded, moisture remains trapped, creating an environment for pathogens like tip blight to take hold.
Overcrowding also causes a lack of sunlight penetration to the lower branches. Arborvitae require sunlight to maintain dense, green growth, and when packed tightly, lower portions become shaded, turning brown and sparse. This results in “leggier” trees where dense foliage only remains near the top. Furthermore, closely planted root systems compete intensely for water and nutrients, which stunts growth and leads to less vigorous trees overall.
Determining Spacing Based on Planting Goals
The specific distance between arborvitae depends entirely on the desired outcome for the planting. A primary consideration is whether the goal is an immediate, seamless hedge or a more natural, specimen-focused look. The intent determines the spacing strategy before considering the specific cultivar’s mature size.
For a tight, formal hedge that quickly merges into a solid wall of green, arborvitae are planted closer together. This encourages the immediate interlocking of branches, creating a dense barrier sooner. However, closer spacing requires higher maintenance, as frequent pruning is necessary to maintain shape and air flow.
A loose privacy screen or natural boundary requires wider spacing, allowing each tree to develop its individual, conical shape. Wider spacing ensures trees receive more all-around sunlight, promoting a fuller, healthier appearance. When the goal is to highlight the tree as a singular specimen, spacing must be maximized to accommodate the cultivar’s full mature width.
Specific Planting Distances for Popular Arborvitae Varieties
The most reliable way to calculate planting distance is to use the mature width of the specific cultivar as the base measurement. For a hedge or screen, the general rule is to plant the trees at a distance that is equal to half to two-thirds of their expected mature width. Planting distance is based on the mature width, not the eventual height.
‘Emerald Green’ Arborvitae
The popular ‘Emerald Green’ arborvitae (Thuja occidentalis ‘Smaragd’) typically reaches a mature width of 3 to 4 feet. For a dense, formal privacy hedge, these should be spaced 2 to 3 feet apart, measuring from the center of one trunk to the center of the next. If the goal is a more relaxed screen that will take a few more years to merge, a spacing of 4 feet apart is recommended, and for individual specimen planting, 5 feet is appropriate.
‘Green Giant’ Arborvitae
For the fast-growing ‘Green Giant’ arborvitae (Thuja plicata x standishii), which can spread 10 to 15 feet wide at maturity, the spacing is significantly wider. For a dense, uniform hedge or barrier, ‘Green Giants’ are best planted 5 to 8 feet apart. If the planting is intended as a windbreak or a more natural, less formal screen, a spacing of 8 to 12 feet allows each tree ample room to develop its full size and shape.
Other Common Varieties
Other common varieties, such as ‘Techny’ (Thuja occidentalis ‘Techny’), which grows 5 to 6 feet wide, should be planted 3 to 4 feet apart for a solid hedge. The cultivar ‘Nigra’ has a similar mature width to ‘Techny’, and a 3-to-5-foot spacing is recommended for a dense screen. When in doubt, planting at the wider end of the recommended range for a hedge will increase air circulation and reduce the chance of disease, even if it delays canopy closure slightly.