Arborvitae (Thuja) is a favored evergreen in North American landscaping due to its dense, year-round foliage. These versatile trees and shrubs are frequently selected for privacy screens, windbreaks, or as attractive individual specimens. The long-term health and desired growth of an arborvitae are largely determined by the initial choice of its planting location. Selecting the correct site addresses the plant’s fundamental biological needs and mitigates future environmental damage.
Sunlight and Soil Requirements
Arborvitae perform best with full sunlight, defined as a minimum of six hours of direct sun exposure daily. While they tolerate partial shade, insufficient light results in sparse foliage and a thinning structure. Planting in a location receiving less than four hours of sun often compromises the plant’s natural density, causing lower branches to fail to fill out.
The root system requires consistently moist yet well-drained soil. Arborvitae strongly dislike perpetually waterlogged conditions, which lead to root rot and plant failure. Conversely, excessively sandy soil that drains too quickly may cause chronic dehydration, especially during dry periods.
The ideal planting medium is rich, loamy soil that retains moisture without becoming heavy or compacted. Arborvitae thrive across a relatively broad pH range, preferring conditions that are slightly acidic to moderately alkaline (6.5 to 8.0). For sites with heavy clay or poor drainage, amend the native soil with organic materials like compost before planting. This preparation improves aeration and ensures the newly installed root ball establishes itself effectively.
Strategic Spacing for Future Growth
Proper spacing is determined by the specific variety chosen and the intended purpose, whether for a dense hedge or a standalone specimen. For the popular, columnar ‘Emerald Green’ variety, which matures to three to four feet wide, planting them two to three feet apart rapidly creates a seamless privacy screen. If the goal is a more defined look where individual plants are distinguishable, four to five feet of spacing is appropriate.
The much larger ‘Green Giant’ cultivar, which can reach 12 to 15 feet wide, requires significantly more room. For a tight, imposing screen, a minimum distance of five to six feet between trunks is recommended. To allow the trees to grow to their maximum potential, spacing them eight to ten feet apart is necessary.
It is necessary to consider the mature spread of the tree when locating it near permanent structures such as foundations, driveways, or walkways. Planting a large variety too close to a house can lead to structural interference from the widening canopy and root system over time. Planting them too near pavement can result in limited light and air circulation, potentially causing the side facing the structure to brown.
Guarding Against Environmental Stressors
Even with ideal sunlight and soil, certain site-specific environmental factors can lead to long-term decline. A major threat is winter burn, which occurs when the plant loses moisture faster than it can be replenished because the ground is frozen. Planting arborvitae in locations fully exposed to intense winter sun and harsh, drying winds greatly increases this desiccation risk.
The foliage is susceptible to browning on sides facing south or southwest, where winter sun exposure is strongest. Positioning the plants with protection from wind tunnels or bright, exposed corners helps them retain moisture during colder months. Also, avoid planting in areas where water naturally collects, such as at the bottom of a steep slope or beneath a gutter downspout.
This site-specific pooling of water can easily create the constantly soggy conditions that promote root rot, regardless of the overall soil type in the yard. Another significant hazard is the proximity to surfaces treated with de-icing salts during winter. Salt spray and runoff from roads, sidewalks, and driveways are toxic to arborvitae roots and foliage. The sodium content in the soil can cause severe foliage browning and long-term root stress, making it advisable to maintain a generous distance from areas where chemical de-icers are regularly used.