Arborvitae (genus Thuja) is a popular choice for creating a dense, year-round living privacy screen or hedge. Establishing a continuous wall of green requires careful consideration of planting distance. Spacing directly influences the time it takes for individual plants to merge and form a thick, impenetrable barrier.
Identifying Your Arborvitae Variety
The correct planting distance depends entirely on the mature size and growth characteristics of the chosen cultivar. The two most common varieties used for screening are the narrow, columnar Thuja occidentalis ‘Emerald Green’ and the significantly broader, faster-growing Thuja plicata ‘Green Giant’. Understanding their natural habits is the first step in planning a successful hedge.
The ‘Emerald Green’ arborvitae is an excellent choice for smaller yards or narrow spaces because its mature width is typically a modest three to four feet. This variety maintains a tight, pyramidal shape and has a relatively slow growth rate, usually adding six to twelve inches of height per year. Its slower growth means it will require less frequent pruning to maintain a formal, dense appearance.
In contrast, the ‘Green Giant’ is a hybrid cultivar known for its rapid growth, often increasing in height by three to five feet annually. At full maturity, it can reach a substantial width of twelve to fifteen feet, making it suitable for large properties where a tall, wide screen is desired. These differences in mature spread and growth rate determine how closely you can plant them without causing long-term health issues from overcrowding.
Determining Optimal Spacing for Immediate vs. Long-Term Privacy
The decision of how far apart to plant arborvitae requires balancing the desire for immediate privacy against the long-term health of the hedge. Planting closer together accelerates the formation of a solid screen but can lead to competition for resources and reduced air circulation over time. Conversely, wider spacing allows each plant to reach its full potential size with less maintenance, though it delays the complete visual block.
For the narrow ‘Emerald Green’ variety, standard spacing that permits full, uncrowded growth is approximately three to four feet between the centers of the plants. To achieve a tight, immediate privacy screen, a closer spacing of two and a half to three feet is often recommended. Planting at this tighter distance means the hedge will merge within a few years, but it will require consistent shearing to manage density and prevent the lower branches from thinning out.
The dramatically larger ‘Green Giant’ requires significantly more space to thrive. For a dense, quick-forming hedge, planting them five to six feet apart on center is the most common recommendation. This distance allows the fast-growing trees to quickly fill the gaps and create a cohesive wall. If the goal is a lower-maintenance, more natural-looking screen where the individual plants are fully showcased, a wider spacing of eight to ten feet is more appropriate.
The size of the plant purchased also influences the initial spacing decision. Larger container plants provide more immediate coverage and can sometimes be spaced slightly wider than smaller stock. However, spacing must always be based on the cultivar’s mature width to prevent chronic overcrowding and ensure long-term vigor.
Establishing the Hedge: Planting Depth and Soil Preparation
Once spacing is determined, planting must be executed with precision, especially regarding depth. Arborvitae are susceptible to root rot if planted too deeply, a common error. Locate the root flare, the slight widening where the trunk meets the roots, and ensure this point is level with or slightly above the surrounding soil line.
The planting hole should be dug two to three times wider than the root ball, but only as deep as the root ball itself. This wide hole provides ample space for the shallow, fibrous root system to spread laterally into loosened soil, encouraging rapid establishment. Before backfilling, it is helpful to gently loosen any tightly bound roots on the exterior of the root ball to prevent them from continuing to circle.
Arborvitae thrive in moist, well-draining soil, making proper soil preparation necessary, particularly in areas with heavy clay. Amending the backfill soil with organic matter, such as compost, can significantly improve drainage and structure. After setting the plant and backfilling the hole, a thorough watering is required to settle the soil and eliminate air pockets. This minimizes transplant shock and encourages initial root-to-soil contact.
Pruning and Care for Maximum Density
Maintaining a dense, full privacy hedge over time depends heavily on consistent and correct pruning techniques. Unlike many deciduous plants, arborvitae should not be cut back into old, brown wood, as new growth will not regenerate from those sections. Pruning should focus on the new, green growth at the tips of the branches to stimulate the formation of side shoots, which increases density.
The proper shape for a hedge is slightly wider at the bottom than at the top, creating a gentle taper. This technique ensures that sunlight can reach the lower branches, preventing them from thinning and turning brown. Pruning or shearing the sides lightly should be done in late winter or early spring before the new growth flush begins, or light trimming can occur in late spring after the initial growth has matured.
New hedges require consistent attention to watering, especially during the first year of establishment. Deep, regular watering encourages the roots to grow outward and downward, creating a resilient plant. Applying a balanced, slow-release granular fertilizer in the early spring can also support vigorous growth, helping the plants quickly fill in the gaps and maintain their lush, dense foliage.