Arborvitae (Thuja) is a popular choice for creating living privacy screens. Its appeal stems from its rapid growth habit and dense, columnar foliage that provides year-round visual obstruction. Understanding the proper planting and care techniques ensures the development of a healthy, uniform hedge. Following specific guidelines from selection through long-term maintenance will maximize the potential for a successful, lush barrier.
Selecting the Best Variety and Spacing for a Screen
Choosing the correct cultivar is the first step in establishing an effective privacy screen. Some varieties are naturally pyramidal and slender, making them suitable for narrow spaces where lateral growth must be contained. Other types exhibit a broader, faster-growing habit, which is ideal for achieving a thick, substantial barrier in open areas.
To form a continuous, impenetrable hedge, Arborvitae must be planted at a distance that allows their mature canopies to meet and overlap slightly. The general rule for calculating the correct spacing is to take the plant’s projected mature width and divide that measurement in half or two-thirds. If a variety is expected to reach 10 feet wide, planting them 5 to 6 feet apart center-to-center ensures they eventually merge into a solid wall of foliage.
Planting too closely may lead to overcrowding, which restricts air circulation and sunlight penetration to the lower branches, causing them to thin out. Conversely, planting too far apart will result in gaps between the trees for many years, defeating the immediate purpose of a privacy screen. The appropriate spacing balances the need for immediate density with the long-term health and mature size of the evergreen.
Preparing the Planting Site
Before planting, assess the site’s drainage, as Arborvitae do not tolerate standing water or saturated roots. A simple test involves filling the planned hole with water; ideal soil should drain completely within a few hours. If the site has heavy clay soil, amending the backfill with compost or aged organic matter will improve the soil structure and porosity.
The planting hole should be excavated to be at least two to three times the diameter of the root ball, but it must not be dug deeper than the height of the root ball itself. Planting too deep is a common error that suffocates the root collar, leading to eventual decline. The goal is to encourage lateral root growth into the surrounding native soil, establishing a strong anchor for the tall, upright plant.
Loosening the soil around the perimeter of the planting area is just as beneficial as amending the soil in the hole. Using a shovel or a garden fork, disrupt the soil structure in a wide circle around where the tree will be placed. This action breaks up any compacted layers, enabling new roots to easily extend outward beyond the confines of the original planting hole.
Installing the Arborvitae
Once the site is prepared, carefully remove the Arborvitae from its container, taking care not to damage the trunk or branches. If the roots are tightly coiled or circling the outside of the soil mass, they must be gently loosened or scored with a sharp tool. This process interrupts the circling pattern and signals the roots to begin growing outward into the prepared soil.
The root ball should be placed into the hole so that the root flare—the point where the trunk widens and transitions into the root system—is slightly above or level with the surrounding grade. Planting the tree even a few inches too low can lead to moisture collection around the trunk, making the plant susceptible to rot and stress. This shallow placement is the single most important factor for long-term tree health.
Begin backfilling the hole with the prepared soil mixture, working it carefully around the sides of the root ball to eliminate large air pockets. Air pockets can dry out the roots and hinder proper establishment, so gently tamping the soil helps settle the dirt. Avoid heavy compaction, as this restricts oxygen exchange necessary for healthy root function.
After the hole is fully backfilled, create a small ring of soil around the perimeter of the planting area to form a watering basin. The tree should then receive a deep, thorough watering immediately after installation. This initial soaking settles the soil, hydrates the roots, and initiates the tree’s transition into its new location.
Long-Term Care for Density and Height
Establishing a consistent watering routine is necessary for the first one to two growing seasons. During dry periods, especially the first summer, deep watering is more beneficial than frequent, shallow sprinkling, as it encourages roots to grow deeper into the soil. Once the plants are established, they become more resilient but still benefit from supplemental water during extended droughts.
Applying a layer of organic mulch helps conserve soil moisture and moderate soil temperature fluctuations around the root zone. A layer of mulch two to three inches deep across the planting area is sufficient, but keep the mulch several inches away from the actual trunk of the plant. Piling mulch directly against the bark can trap moisture and create an environment conducive to disease and pests.
To achieve the desired dense, uniform hedge, light pruning, or “tipping,” encourages lateral branching and foliage thickness. Shearing or clipping the new growth at the top and sides of the plants, typically in late spring or early summer, stimulates the tree to fill out rather than focusing solely on height. This technique should be performed minimally, only removing a few inches of new growth, as Arborvitae generally do not respond well to heavy pruning into old wood.