The Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’) is a favored narrow evergreen known for its bright green foliage and naturally pyramidal shape. Its dense, vertical growth habit makes it an excellent choice for creating privacy screens, hedges, or adding a structured element to the landscape. The most significant factor determining the plant’s mature health and aesthetic quality is correct initial spacing. Ignoring this step can lead to issues with air circulation, disease, and overall plant form as the arborvitae matures.
Determining Planting Goals
Before planting, the intended function of the arborvitae must be defined, as this goal dictates the required distance between plants. The most common objective is establishing a dense, seamless privacy hedge, which requires the plants to grow into each other to form an uninterrupted green wall. This relies on the canopies touching or slightly overlapping at their mature width to achieve visual blockage.
A second goal involves creating a staggered screen, where the plants are close enough to provide privacy but maintain distinct, individual forms. This spacing allows for more air and light penetration between the trees while still offering substantial screening.
Finally, the arborvitae may be planted as a standalone specimen. This objective is to allow the plant to reach its full, natural width and height without interference, maximizing its pyramidal structure and requiring the most generous allocation of space.
Specific Spacing Measurements
For creating a dense, continuous privacy hedge, the optimal planting distance is between 2 to 2.5 feet, measured from the center of one trunk to the center of the next. This close spacing ensures the plants’ mature widths (averaging 3 to 4 feet) intersect quickly, forming the desired screen. This density accelerates hedge creation but necessitates monitoring for disease due to reduced air circulation.
When a staggered screen is the goal, increasing the center-to-center distance to 3 feet is appropriate. This increase encourages better lateral growth and allows each arborvitae to develop a more robust base before the canopies merge. This intermediate distance balances privacy needs with improved plant health.
To maximize the Emerald Green as a specimen plant, the distance must be based on its full mature width, requiring 4 to 5 feet of space on all sides. Planting too far apart, such as 6 or 7 feet for a hedge, results in persistent gaps that take many years to fill. Conversely, planting closer than 2 feet restricts light and airflow, creating a humid microclimate that increases susceptibility to fungal diseases like Cercospora leaf blight.
Essential Planting Technique
Once the appropriate spacing has been marked out, the physical planting technique determines the plant’s long-term success. The planting hole must be dug wide—at least two to three times the diameter of the root ball—but no deeper than the height of the root ball itself. The wider hole encourages the quick expansion of fine root hairs into the surrounding native soil, while the correct depth prevents the plant from settling too low.
Before placing the arborvitae, any materials around the root ball must be addressed; for balled-and-burlapped plants, the twine and the top portion of the wire basket and burlap should be removed or cut away completely once the plant is in the hole. For container-grown stock, the roots often need to be scored or separated to break up circling patterns that can girdle the trunk.
Ensuring the root flare—where the trunk begins to widen before meeting the roots—is level with or slightly above the finished grade of the surrounding soil is the primary technical detail. Planting too deeply is a common error that suffocates roots and leads to chronic health decline. The hole should be backfilled with the original soil, avoiding excessive amendments that can create a “bathtub effect” where water fails to drain properly. Gently tamping the soil removes large air pockets and ensures firm contact between the roots and the earth.
Post-Planting Care for Establishment
Immediate and consistent post-planting care helps the Emerald Green Arborvitae overcome transplant shock. The first step is a thorough and deep watering immediately after planting to settle the soil and fully hydrate the root ball. For the first two growing seasons, the soil must be kept consistently moist but never waterlogged, often requiring monitoring every few days during hot or windy weather.
Applying a layer of organic mulch, such as shredded bark or wood chips, helps regulate soil temperature and retain moisture, which is beneficial for root development. This layer should be maintained at a depth of two to three inches, extending out to the drip line of the canopy. Keep the mulch pulled back several inches from the trunk base to prevent moisture buildup and subsequent rot or fungal issues.
During the initial establishment phase, the focus should be on root growth rather than top growth, meaning fertilization is discouraged for the first year. Introducing high-nitrogen fertilizers can stress the plant by forcing foliage development when the root system is not yet capable of supporting it. Signs of transplant shock, such as browning or wilting, should be monitored and usually indicate a need to check soil moisture levels.