The Arborvitae, a species of the genus Thuja, is a highly favored evergreen for creating natural boundaries and privacy hedges. Determining how many you need for a 50-foot stretch depends entirely on the specific variety selected, as mature size dictates planting distance. The goal is to create a dense, continuous green wall, requiring the mature canopies of adjacent trees to slightly overlap. This article guides you through selecting the right cultivar and calculating the exact number of trees for your 50-foot screen.
Selecting the Right Arborvitae Variety
The choice of arborvitae variety is the most important factor determining spacing and total plant count. Different cultivars have vastly different mature widths and growth rates, impacting how quickly they fill the space. Selecting a plant based on its final size prevents overcrowding or waiting too long for a complete screen.
The two most popular choices are the ‘Emerald Green’ (Thuja occidentalis ‘Smaragd’) and the ‘Green Giant’ (Thuja standishii x plicata). ‘Emerald Green’ is a narrow, columnar tree that typically matures to a width of only 3 to 4 feet, making it ideal for smaller yards or tighter spaces. This variety is a slower grower, gaining less than a foot per year, but it maintains a dense, vibrant green color throughout the winter.
In contrast, the ‘Green Giant’ is a vigorous hybrid known for its rapid growth, often adding 3 to 5 feet in height annually. This cultivar develops into a much larger specimen, reaching a mature width of 12 to 15 feet. Using the ‘Green Giant’ requires significantly wider spacing, meaning fewer plants are needed to cover the 50-foot distance, provided you have the space to accommodate its substantial size.
Calculating Your Spacing and Quantity Needs
The rule for creating a dense privacy hedge is to space the trees so their mature widths overlap by 1 to 2 feet. This overlap ensures a continuous, sight-blocking barrier once the plants reach full size. The formula to determine the quantity is: (Total Hedge Length in Feet / Desired Spacing) + 1, with the “+1” accounting for the final tree at the end of the run.
For the narrow ‘Emerald Green’ arborvitae (3 to 4 feet mature width), a recommended dense spacing is 3 feet apart, measured center-to-center. Applying this to the 50-foot section: (50 feet / 3 feet) = 16.67, rounding up to 17. Adding the final tree means 18 plants are needed for the 50-foot row.
The wider ‘Green Giant’ arborvitae (12-to-15-foot mature spread) requires 5 to 6 feet of spacing for a dense screen. Using 6-foot spacing yields: (50 feet / 6 feet) = 8.33, rounding up to 9. This results in 10 plants needed. Planting too closely can lead to competition for resources and poor air circulation, increasing the risk of disease.
Installation: Preparing the Site and Planting
Successful establishment begins with proper site preparation. Arborvitae require well-draining soil and will not tolerate standing water, which causes root rot. Before digging, loosen the native soil to enhance drainage, especially if it is heavy clay. Amending the soil with organic matter, like compost, improves the growing environment for the new roots.
The planting hole must be two to three times wider than the root ball, but only as deep as the root ball itself. Placing the tree slightly high ensures the top of the root ball sits level with or slightly above the surrounding grade. This prevents water from pooling around the trunk and allows for natural settling without burying the root flare, a common cause of decline.
After placing the tree, backfill the hole with the amended soil, gently tamping it down to remove large air pockets. Water each newly planted arborvitae thoroughly to settle the soil around the root system. This initial watering reduces transplant shock and starts the hydration process.
Long-Term Care for Optimal Growth and Density
The first year is crucial for establishing a strong root system. Newly planted trees require consistent moisture, meaning deep watering two to three times a week for the first few months. The goal is to keep the soil consistently moist, but never saturated, monitoring the soil to avoid overwatering.
Once established, the plants tolerate drier conditions but benefit from supplemental watering during drought. Applying a 2 to 3-inch layer of organic mulch around the base of each tree helps regulate soil temperature, retain moisture, and suppress weed growth. Keep the mulch several inches away from the trunk to prevent moisture buildup and stem rot.
Arborvitae require minimal pruning to maintain their natural shape, but light shearing encourages a denser, more formal appearance. The best time for trimming is late winter or early spring before new growth appears, or in late spring after the initial flush. Avoid cutting back into the older, brown wood, as these evergreens may not regrow foliage from that section.