Arborvitae are evergreen conifers highly valued for their dense foliage and distinct pyramidal or columnar shapes. They are a favored choice among homeowners and landscapers looking to establish a privacy screen or windbreak quickly. The pursuit of the fastest-growing variety is common, as a rapid rate of growth translates directly into a faster-achieved barrier. However, the term “fastest” is relative, depending significantly on the specific cultivar chosen and the conditions provided in the landscape.
Direct Comparison: The Fastest Growing Varieties
When selecting an arborvitae for maximum growth speed, the hybrid ‘Green Giant’ (Thuja plicata x standishii) stands out as the clear leader. This cultivar is known for its exceptional vigor, capable of adding between three and five feet of vertical growth annually once it is well-established. Its hybrid genetics, combining the hardiness of Japanese arborvitae with the size of the Western Red Cedar, give it a significant advantage in growth potential over other common varieties.
The ‘American Pillar’ (Thuja occidentalis) also offers rapid growth, gaining up to three feet per year. For comparison, the popular ‘Emerald Green’ (Thuja occidentalis ‘Smaragd’) has a much slower growth habit, typically adding only six to twelve inches in height annually. While the ‘Emerald Green’ is favored for its narrow, compact shape and low maintenance, its growth rate makes it unsuitable for anyone prioritizing quick privacy.
The genetic potential of a cultivar dictates its maximum possible growth rate, making the ‘Green Giant’ the most reliable choice for a high-velocity screen. Cultivars like ‘Hetz Wintergreen’ offer an intermediate rate, often growing over two feet per year, striking a balance between speed and a more manageable mature size.
Environmental Factors Affecting Growth Rate
Achieving the maximum growth potential of any arborvitae relies heavily on providing optimal environmental conditions. Sunlight is a primary accelerator for growth, with trees performing best and developing the densest foliage when they receive at least six hours of direct sun daily. Arborvitae planted in excessive shade will often exhibit thinner, sparser growth and a significantly reduced annual growth rate.
The characteristics of the soil are another factor, particularly its ability to drain water effectively. Arborvitae prefer moist soil but are highly susceptible to root rot if they are planted in perpetually waterlogged conditions, such as heavy clay or low-lying areas. Well-draining soil prevents root stress and allows the tree to focus its energy on shoot elongation. Furthermore, the tree’s suitability to its USDA Hardiness Zone determines its ability to thrive, as varieties like ‘Green Giant’ are more adaptable to heat and humidity than species like Western Red Cedar.
Optimizing Planting for Rapid Establishment
The first year after planting is important because the tree dedicates its resources to establishing a robust root system before accelerating upward growth. To maximize this initial establishment velocity, the planting hole should be dug two to three times wider than the root ball, but no deeper. This width provides loosened soil for the roots to expand into quickly, while the correct depth prevents the tree from settling too low and suffocating the root collar.
Backfilling the hole with the original native soil, potentially amended with a small amount of compost, and ensuring the top of the root ball is level with or slightly higher than the surrounding grade is a best practice. After planting, a deep, thorough watering settles the soil and eliminates air pockets around the roots.
Applying a two to three-inch layer of organic mulch around the base of the tree, keeping it several inches away from the trunk, helps to retain soil moisture and regulate temperature. Consistent watering is necessary during the first growing season; the soil must be kept moist, not saturated, to encourage the root system to spread rapidly and support the explosive growth expected in subsequent years.