The Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’) is a highly popular narrow evergreen cultivar prized for its dense, columnar growth habit. This selection is frequently used in landscapes to create year-round privacy screens and hedges, especially in tighter spaces. Understanding the growth rate of this specific plant is crucial for planning a landscape, as its speed directly impacts the time required to achieve a desired screening height. This article details the expected growth trajectory and the variables that influence how quickly the tree reaches its mature size.
Baseline Annual Growth and Mature Size
The Emerald Green Arborvitae is classified as a slow to moderate grower, with a predictable and steady annual vertical increase. Under favorable conditions, the expected annual growth rate ranges from about six inches to one foot per year. This rate is considered semi-dwarf compared to other arborvitae varieties, contributing to its low-maintenance appeal.
The mature height of the Thuja occidentalis ‘Smaragd’ typically falls between 10 and 15 feet, with a narrow width of about three to four feet. The slow horizontal growth, often only one to two inches annually, maintains the characteristic slender, pyramidal shape without constant shearing. Due to this moderate growth speed, a young arborvitae usually takes approximately five to seven years to reach a functional screening height of six feet.
The initial growth period focuses heavily on root establishment before significant vertical growth is observed. Once the root system is well-anchored, the tree begins to put on its more consistent, vertical growth. This established growth pattern makes the tree a reliable, long-term option for hedges.
Key Environmental Factors Affecting Growth Speed
The actual growth speed of an Emerald Green Arborvitae is heavily influenced by environmental conditions. Optimal growth requires a location that receives full sun, meaning at least six hours of direct sunlight daily. Planting the tree in an area with too much shade will significantly slow the growth rate and result in sparse, less dense foliage, compromising its screening function.
Soil quality and proper drainage are equally important, as the tree thrives in moist, well-draining soil types. Heavy clay that retains too much water will restrict the root system’s ability to expand, leading to stunted growth or root health issues. Consistent moisture is particularly important during the first few growing seasons while the plant establishes its root network.
Drought stress is a major factor that can halt growth entirely, especially in younger trees. Although established plants have some drought tolerance, prolonged dryness causes the plant to prioritize survival over new growth. The tree performs best within its optimal hardiness range, generally USDA Zones 3 through 8, where temperatures and climate patterns support its growth cycle.
Cultivation Techniques to Promote Maximum Growth
Specific cultivation practices encourage the Emerald Green Arborvitae to achieve the maximum growth rate its genetics allow. Applying a balanced, slow-release granular fertilizer, such as a 10-10-10 formulation, in the early spring provides the necessary nutrients to fuel the season’s new growth. While these trees are not heavy feeders, an annual application supports overall health and vigor, which translates to faster development.
The application of organic mulch around the base of the plant is an effective technique to optimize the root zone environment. A layer about three to four inches deep helps to regulate the soil temperature and reduces water evaporation, ensuring the consistent moisture the roots require. It is important to keep the mulch pulled back a few inches from the trunk to prevent moisture buildup that could encourage disease or pests.
Pruning techniques should be carefully managed when height is the primary goal. Heavy shearing should be avoided to preserve vertical growth. Light tip pruning of the newest growth in early spring can stimulate branching and encourage a denser canopy. Maintaining diligent watering and feeding during the first few years sets the foundation for accelerated visible growth in subsequent years.