Thuja, commonly known as Arborvitae, is a popular evergreen conifer frequently chosen for creating dense privacy screens or as a stately landscape specimen. The success and longevity of this plant depend heavily on correct planting techniques that establish a healthy root system from the start. Understanding the proper procedure ensures the tree can efficiently access water and nutrients, allowing it to thrive.
Preparing the Planting Site and Thuja
Selecting the appropriate location is the first step toward a healthy Thuja, which generally performs best when receiving full sun to partial shade (a minimum of four to six hours of direct sunlight daily). The site must also offer excellent drainage, as Thuja can develop root rot if roots are left sitting in standing water. If the planting site contains heavy clay soil, drainage can be improved by incorporating organic material, such as well-aged compost, into the native soil. This amendment enhances the soil structure, allowing water to pass through while retaining sufficient moisture.
The ideal timing for planting Thuja is in early spring or early fall, when the weather is cooler but the ground is not yet frozen. Planting during these periods allows the tree to establish its root system without the stress of summer heat or winter cold. Before planting, thoroughly hydrate the root ball by soaking it in water for at least an hour. A well-moistened root ball prevents the fine roots from drying out and eases their transition into the surrounding soil.
Executing the Planting Procedure
The size and depth of the planting hole are defined to promote outward root growth. The hole should be dug two to three times wider than the diameter of the root ball, but its depth must be equal to or slightly less than the root ball’s height. Planting too deeply is a common error that can suffocate the roots and lead to decline. The tree’s root flare (the point where the trunk begins to broaden) must remain visible at or slightly above the final soil grade after planting.
Once the hole is prepared, inspect the root ball for any circling or tightly wound roots. These roots should be gently teased apart or scored lightly with a knife to encourage them to grow outward. For balled-and-burlapped trees, completely remove any wire baskets. The burlap should be cut away from the top third of the root ball and folded down into the hole, as leaving these materials wrapped around the roots inhibits growth and prevents proper establishment.
With the tree positioned correctly, backfill the hole using the native soil, mixing in any prepared compost. Fill the hole only halfway and gently tamp the soil down with your hands or a tool handle to eliminate large air pockets. Avoid heavy tamping with your feet, which can compact the soil excessively and restrict oxygen flow to the roots. Finish filling the hole to the level of the root flare, ensuring no soil is piled against the trunk.
After backfilling, construct a small ring or berm of soil around the outer edge of the planting hole. This temporary saucer helps contain water directly over the root zone during the initial watering phase. Provide a thorough, deep watering until the entire area is saturated and the water drains slowly away. This first watering settles the soil around the roots.
Establishing Post-Planting Care Routines
The first one or two growing seasons are dedicated to establishing a robust root system, requiring consistent monitoring of soil moisture. Newly planted Thuja need deep watering once or twice a week, depending on local weather conditions, rather than frequent, shallow sprinklings. The goal is to keep the soil consistently moist but never waterlogged, encouraging roots to grow downward. To check moisture, insert a finger or meter two inches into the soil; if it feels dry at that depth, it is time to water again.
Applying a layer of organic mulch is beneficial for moisture retention and temperature regulation. Spread a two to three-inch layer of wood chips or shredded bark over the planting area, extending out to the drip line. Keep the mulch ring several inches away from the Thuja trunk to prevent moisture buildup, which can lead to fungal issues and rot at the root flare.
During the initial establishment period, the tree’s energy should focus on root development, meaning fertilization is unnecessary and can sometimes be detrimental. Most native soils contain enough nutrients to support new growth, and adding fertilizer can burn delicate new roots. If a soil test indicates a deficiency, a slow-release, balanced fertilizer can be applied in the second year, ideally in early spring.
Protecting Thuja from Environmental Stressors
Thuja, particularly in colder climates, is susceptible to winter burn, which occurs when the plant loses moisture through its foliage faster than its frozen roots can replenish it. To minimize desiccation, ensure the tree receives a deep soaking in late fall before the ground freezes. Applying an anti-desiccant spray to the foliage in late fall (when temperatures are above freezing) can help by creating a protective layer that reduces water loss.
Deer browsing presents a significant threat to Thuja, as it is a favored food source for white-tailed deer, especially when other vegetation is scarce. Physical barriers, such as netting or temporary fencing, are the most reliable methods for protection against grazing. While repellents can be used, they require consistent reapplication and are often less effective under heavy deer pressure.
Regularly inspecting the foliage for signs of pests or disease is a routine maintenance measure. Common issues include bagworms (which create distinct, spindle-shaped bags on the foliage) and spider mites (which thrive in hot, dry conditions). Early detection allows for targeted treatment, such as hand-picking bagworms or applying a horticultural oil to control mites, preventing widespread damage.