The Green Giant Arborvitae (Thuja plicata x standishii) has become an exceptionally popular choice for establishing fast-growing privacy screens and hedges. This hybrid cultivar is prized for its rapid growth rate, often exceeding two feet per year under ideal conditions. Achieving vigorous growth and ensuring the plant’s long-term health depends on selecting the correct time and employing proper technique during the initial transplanting process. Establishing a strong root system early is the foundation for the plant’s future success in the landscape.
The Optimal Planting Window
The most favorable periods for planting occur when the soil is warm enough to encourage root growth but air temperatures remain moderate. Late spring, generally after the final frost has passed, offers this ideal combination. The warming soil stimulates root cell division, allowing the plant to establish itself before the intense heat of summer arrives. This strategic timing allows the plant to focus its limited transplant energy entirely on subterranean development rather than coping with environmental stress.
A second, equally suitable window opens in the early fall, typically spanning from late August through September in many temperate regions. Planting during this time gives the arborvitae six to eight weeks to establish fine feeder roots before the ground freezes solid. Cooler ambient air temperatures reduce moisture loss through transpiration. Meanwhile, the soil retains enough residual warmth from the summer to promote active root growth necessary for anchoring.
Successful establishment is most efficient when soil temperatures are consistently between 50 and 65 degrees Fahrenheit. For gardeners in USDA Hardiness Zones 5 through 7, this translates to the defined periods of late spring and early fall. The moderate weather inherent to these seasons usually brings consistent rainfall, lessening the initial burden of supplemental irrigation and supporting the delicate process of root regeneration.
Seasonal Weather Considerations
Transplanting during peak summer months should be avoided due to the significant risk of heat stress and desiccation. When air temperatures consistently exceed 85 degrees Fahrenheit, the plant’s rate of transpiration increases, demanding far more water than a newly disturbed root system can efficiently supply. This imbalance often leads to foliage scorching and severe transplant shock, which can permanently stunt growth or lead to death.
Deep winter presents an opposite but equally damaging set of challenges for the arborvitae. Planting into frozen ground prevents immediate root establishment, leaving the plant unable to draw moisture from the soil. Repeated freeze-thaw cycles can lead to frost heave, where the expanding and contracting soil lifts the root ball out of the ground, exposing roots to drying winds and low temperatures.
The primary goal is to avoid periods when the plant must expend energy simply surviving the environment rather than growing new roots. Any period where the ground is frozen solid or where daytime temperatures regularly climb above 90 degrees Fahrenheit is considered an unfavorable time for transplanting. Postponing planting until conditions moderate significantly increases the probability of survival and vigorous growth.
Essential Steps for Successful Transplanting
Proper site preparation is just as important as selecting the right season for planting. The planting hole should be dug two to three times wider than the root ball’s diameter, but no deeper than the root ball itself. Digging a wide hole loosens the surrounding soil, allowing new roots to easily extend horizontally into the landscape rather than encountering compacted earth.
Before placing the plant, completely remove the burlap, wire cage, or container. Inspect the root ball for any encircling or matted roots. Circling roots must be gently loosened or physically scored with a knife in several places to encourage them to grow outward. This action prevents the roots from self-girdling the trunk and strangling the plant as it matures over time.
Backfill the hole using the native soil that was removed, avoiding excessive amendments, which can discourage roots from leaving the prepared area. After the soil is firmed gently, the arborvitae requires immediate and deep watering to settle the soil around the roots and eliminate air pockets. This initial saturation is necessary to fully hydrate the plant and initiate the connection between the root system and the surrounding soil environment.