The Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’) is popular for creating dense, narrow hedges and privacy screens. This cultivar is naturally a slow-growing evergreen, typically adding only six to twelve inches of height per year once established. Maximizing its growth potential requires a focused care regimen designed to accelerate its upright development. The following strategies address the environment, nutrition, and management needed to push this plant to its upper growth capacity.
Optimizing the Planting Environment
The foundation for rapid growth begins with the location and preparation of the planting site. Emerald Green Arborvitae needs at least six hours of direct sunlight daily to produce the energy required for vigorous growth. While it tolerates partial shade, insufficient light results in sparser foliage and a significantly slower growth rate.
The soil structure must facilitate both moisture retention and effective drainage. Heavy or compacted clay soil restricts root expansion, limiting top growth. Amending the planting hole with organic matter like pine bark fines can improve soil porosity. When planting a hedge, position trees three to four feet apart. This spacing ensures mature canopies and root systems do not compete for resources and promotes air circulation, which prevents stress and disease.
Targeted Nutritional Support
To encourage stem elongation and dense foliage, a strategic fertilization plan is necessary. Nitrogen (N) is the primary macronutrient responsible for vegetative growth, driving the production of new leaves and branches. Applying a balanced, slow-release granular fertilizer with a slightly higher nitrogen ratio, such as a 16-4-8 NPK blend, provides this boost.
The best time to apply this nutritional support is in the early spring, just before new growth emerges, and again in early to mid-summer. This schedule aligns with the arborvitae’s active growing periods, ensuring nutrients are available when the plant needs them most. Distribute the granules evenly across the root zone, extending out to the drip line, but keep them several inches away from the trunk. This avoids concentrating salts near the stem, which can cause chemical burn and inhibit the plant’s ability to absorb water and nutrients.
Consistent Water Management
Even with optimal sun exposure and fertilization, inconsistent moisture will be the limiting factor for accelerated growth. Newly planted arborvitae require consistent moisture for the first one to two years to establish a deep and widespread root system. During this establishment phase, water deeply two to three times per week, depending on weather conditions, to ensure the entire root ball is soaked.
Deep watering is preferred over frequent, shallow applications because it encourages the roots to grow downward, making the plant more resilient and capable of supporting faster top growth. A good soaking should penetrate the soil to a depth of at least six to eight inches, which can be checked by probing the soil. Signs of water stress, such as browning tips or a general lack of vigor, indicate that the growth rate is being compromised. Applying a three-to-four-inch layer of organic mulch, such as shredded bark, over the root zone helps regulate soil temperature and significantly reduces water evaporation.
Identifying and Eliminating Growth Inhibitors
Several common maintenance errors or external factors can actively suppress the Emerald Green Arborvitae’s growth. One of the most significant inhibitors is aggressive pruning, particularly cutting into the brown, interior wood of the plant, which will not regenerate new foliage. To maintain vertical speed, limit pruning to only light, selective shearing of the green tips to encourage lateral branching and density.
Removing the central leader, known as “topping,” permanently halts vertical growth and forces the plant’s energy into lateral expansion. Pests like spider mites or bagworms can also stress the plant, diverting energy away from growth and toward defense. Early identification and treatment of these issues are necessary to maintain a healthy, rapidly growing specimen. Finally, protecting the base of the tree from mechanical damage, such as nicks from string trimmers or lawnmowers, prevents wounds that can lead to infection and slow the overall growth process.