The Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’) is a highly favored, narrow evergreen cultivar prized for its dense, vibrant foliage and naturally pyramidal growth habit. This tree is predominantly used for creating year-round screening and privacy hedges. Correct spacing is the most important decision when planting these evergreens, directly influencing the long-term health and the ultimate density of the barrier. Proper planning ensures adequate air circulation and light penetration, which are necessary for the arborvitae to thrive.
Determining Planting Distance Based on Goal
The distance between Emerald Green Arborvitae must be dictated by the specific landscaping objective. This cultivar typically matures to a width of three to four feet, which forms the basis for all calculated spacing. Planting distances are measured from the center of the root ball of one plant to the center of the next plant in the row.
Dense Privacy Hedge
For the quickest and most solid visual barrier, a dense privacy hedge requires plants to be placed so their mature widths intersect. This is achieved by planting them on centers three to four feet apart, which is their maximum mature width. This close proximity encourages the plants to quickly form a seamless, uniform green wall. However, denser spacing increases the need for robust air flow to reduce the risk of common fungal diseases.
Specimen Planting
If the goal is to use the arborvitae as individual specimen plants or accents, they need ample room to reach their full, natural size without competition. In this scenario, planting the centers five to six feet apart is recommended. This distance allows each tree to fully expand to its three-to-four-foot width while maintaining a distinct, uncrowded shape. This wider spacing is also suitable for a less dense row or windbreak where space between the plants is acceptable.
Maintaining sufficient space is a mechanical necessity for plant health, not just appearance. Overcrowding blocks sunlight from reaching the lower and interior foliage, causing it to brown and thin out. Lack of air circulation between tightly packed plants creates a humid microclimate that promotes pathogens like bagworms or spider mites. Calculating the required distance ensures each plant receives the resources needed to maintain dense, healthy greenery from the ground up.
Essential Soil and Sunlight Requirements
Before planting, the location must meet the specific environmental needs of the Thuja occidentalis ‘Smaragd’ to support its growth. The most important soil consideration is excellent drainage, as Emerald Green Arborvitae are highly vulnerable to root rot in waterlogged conditions. They prefer a consistently moist, loamy soil structure that allows water to move freely away from the root zone.
The preferred soil pH ranges from slightly acidic to alkaline, ideally between 6.0 and 8.0. While they tolerate a range of soil types, including some clay, the primary focus must remain on ensuring the site does not hold standing water. Testing the soil drainage before planting can prevent long-term establishment problems caused by anaerobic conditions around the roots.
Sunlight is equally important, as it directly impacts the density and color of the foliage. Emerald Green Arborvitae require a minimum of six hours of direct sunlight daily to thrive. Planting in a location that receives less than this minimum results in sparse growth and a reduction in the vibrant green color. Full sun exposure is preferred, although they can tolerate a small amount of afternoon shade, particularly in hotter climates.
Proper Planting Technique
Once the correct spacing and location are determined, proper planting technique is crucial for successful establishment. The planting hole should be dug two to three times wider than the root ball, but no deeper than the height of the root ball itself. Digging a wide hole encourages the roots to grow outward into the surrounding native soil.
The most common mistake when planting is setting the tree too deep, which can lead to stem rot and eventual death. The root flare, where the trunk begins to widen, must be positioned level with or slightly above the surrounding soil surface. If the tree is balled-and-burlapped or in a container, carefully remove all packaging, including burlap or wire, before placing it in the prepared hole.
Before backfilling, inspect the root ball for any roots that are tightly circling the perimeter, which can eventually strangle the tree. These circling roots should be scored or gently loosened and spread out to encourage growth into the surrounding earth. Use the native soil that was excavated to backfill the hole, avoiding heavy amendments which can discourage roots from leaving the planting pit.
After the hole is completely backfilled, gently tamp the soil to eliminate any large air pockets that could dry out the roots. Immediately following this, deeply water the newly planted arborvitae to settle the soil and ensure good contact between the roots and the surrounding earth. This deep initial watering is a fundamental step in reducing transplant shock and beginning the establishment process.
Post-Planting Care
The first year after planting is a period of establishment, and the care provided directly determines the long-term health and growth rate. Newly planted trees require consistent, deep watering to encourage a robust root system. For the first few months, deep watering two to three times per week is often necessary, especially in warm weather.
The soil should be kept consistently moist but never waterlogged, as overwatering is the leading cause of failure for arborvitae. As the plants become established, watering frequency can be reduced, aiming for about one inch of water per week through rainfall or irrigation. Monitoring the soil moisture a few inches below the surface is the most reliable way to assess the need for water.
Applying a layer of organic mulch around the base of the newly planted trees provides multiple benefits for establishment. A layer two to three inches deep helps to:
- Retain soil moisture.
- Stabilize soil temperature.
- Suppress competitive weed growth.
It is important to keep the mulch pulled back several inches from the trunk. Mulch piled against the trunk, often called a “mulch volcano,” traps moisture and encourages rot and pest damage.
During this initial establishment phase, heavy fertilization should be avoided, as the focus needs to be on root growth rather than top growth. If the soil is poor, a light application of a slow-release, balanced fertilizer can be applied, but this is reserved for the second growing season. For the first year, providing adequate water and preventing moisture stress is the primary path to a healthy, established plant.