Thuja, commonly known as Arborvitae, is a popular choice for landscape screening and hedging due to its dense, evergreen foliage. This coniferous tree is widely used for creating natural privacy barriers and windbreaks in gardens across many climate zones. Successful establishment of a newly planted Thuja depends on selecting the correct time for transplanting. Optimal timing allows the root system to grow and anchor itself before the onset of environmental stress.
The Primary Planting Window: Early Spring
The primary period for planting Thuja begins in early spring, immediately after the ground becomes workable following the final hard frost of winter. This is the most advantageous period for planting. This timing allows the tree’s root system to exploit the naturally cool and moist conditions of the soil. Root growth proceeds effectively without the high evaporative stress that comes with warmer air temperatures.
Planting during this window gives the Thuja the entire growing season to establish a robust network of fine root hairs. These roots are necessary for absorbing the substantial amounts of water and nutrients the evergreen requires to survive its first winter. By the time summer heat arrives, the tree is better equipped to handle increased water demand because its roots have had time to settle and spread.
The Secondary Planting Window: Early Fall
Early fall is a strong alternative to spring planting, typically spanning from late August through October, depending on the specific climate zone. During this time, air temperatures begin to moderate, which significantly reduces the rate of water loss from the foliage, thus minimizing transplant shock. The ground, however, retains the warmth accumulated over the summer months.
This combination of warm soil and cooler air encourages active root growth while the top growth slows down. It is important to complete the planting process at least six weeks before the soil is expected to freeze solid in your region. This timeframe ensures the newly planted Thuja develops enough new root mass to sustain itself through winter dormancy.
When Planting Thuja Should Be Avoided
Planting Thuja during mid-summer carries a high degree of risk and should generally be avoided across most regions. The combination of intense heat and low humidity causes the tree’s foliage to lose moisture at a rate faster than its newly disturbed root system can absorb it. This imbalance frequently leads to severe desiccation and transplant failure, a condition often referred to as “browning out.” This is why mid-summer planting is generally discouraged across most regions.
Similarly, planting during the deep winter months is not recommended because frozen ground presents a physical barrier to digging and root establishment. Even if the ground can be broken, the roots cannot grow in frozen soil, leaving the tree unable to take up the necessary water. This inability to absorb moisture can lead to a condition known as winter burn, where cold winds and sun dry out the foliage while the roots remain locked in ice.
Immediate Care After Planting
Immediate and consistent aftercare will determine the tree’s survival. After backfilling the planting hole, provide a deep, thorough soaking of water to settle the soil and eliminate any air pockets around the root ball. This initial application ensures the roots are in direct contact with the soil medium. This step is crucial for successful establishment.
Following the initial watering, apply an organic mulch layer, ideally three to six inches deep, across the root zone to help conserve soil moisture and regulate temperature fluctuations. Ensure the mulch is kept several inches away from the trunk to prevent moisture buildup that could encourage bark decay or pest activity. For the first few months, monitor the soil moisture closely, providing regular supplemental water whenever the top few inches of soil feel dry.