The Green Giant Arborvitae (Thuja standishii x plicata) is an evergreen cultivar known for its rapid growth and dense, pyramidal form, making it suitable for privacy screens. While this hybrid conifer is robust, successful establishment depends entirely on receiving the correct amount of water immediately following planting. Root establishment is a vulnerable period for any transplanted tree. A phased approach, moving from high-frequency initial care to a long-term, deep-soaking method, is necessary to support the tree’s transition to the landscape.
The Critical First Two Weeks
The initial two weeks after planting are the most significant period of stress, requiring a high-frequency watering schedule to prevent the root ball from drying out. Immediately after planting, a thorough, deep soaking is necessary to settle the soil around the roots and eliminate air pockets. For the first three to five days, the tree requires daily watering to maintain consistent moisture in the root zone. Following this, transition to watering every other day for the remainder of the two-week window. The goal is to keep the root ball consistently moist, but not saturated, as soggy soil restricts oxygen flow and can cause root rot.
Monitoring Soil Moisture and Watering Depth
Moving beyond a fixed schedule, assessing actual soil moisture is necessary for the tree’s long-term success. The “finger test” involves pushing a finger two to three inches deep into the soil just outside the root ball. If the soil at that depth feels dry, it is time to water; if it feels cool and moist, irrigation is not yet required. When watering, the technique must shift to deep watering, which encourages roots to grow downward rather than remaining shallow. Applying water slowly and thoroughly saturates the entire root zone, which can extend 12 to 18 inches deep. Using a soaker hose or drip irrigation system placed over the root area is effective, as it delivers water gradually, minimizing runoff and ensuring deep penetration.
Establishing the Root System During the First Growing Season
After the initial two-week period, reduce the watering schedule to encourage roots to stretch into the surrounding soil. For the rest of the first growing season, the Green Giant Arborvitae requires deep watering one to two times per week. The objective is to provide about one inch of water weekly, delivered in a single, prolonged soaking session. Adjust the frequency based on environmental factors; high heat or drought requires temporary increases, while heavy rain or cooler temperatures prompt a reduction. Always guide supplemental watering using the soil moisture test. Continue watering consistently until the ground freezes in late fall or early winter, as this final deep soaking prevents winter desiccation.