The arborvitae, a popular evergreen from the Thuja genus, is prized for its dense foliage and consistent color, making it a favored choice for privacy screens and landscaping. While these trees are generally hardy, their health and survival depend on proper hydration. Arborvitae roots are relatively shallow, making them highly sensitive to soil moisture fluctuations. Maintaining the correct balance of water ensures the tree can establish a strong root system.
Watering Newly Planted Arborvitae
The first one to two growing seasons are critical for establishment, requiring consistent soil moisture. Immediately after planting, the tree needs a deep soaking to saturate the root ball and surrounding soil, eliminating air pockets. For the first few weeks, water daily or every other day to keep the root ball damp, but never waterlogged.
To encourage roots to grow outward into the surrounding native soil, the watering volume must be substantial. After the first month, transition to deep, slow soaks once or twice a week, depending on temperature and rainfall. The “low and slow” method, often using a hose on a slow trickle, ensures the water penetrates several inches deep. For the entire first year, and potentially the second, maintain a slightly moist environment around the young, shallow roots without causing saturation.
Routine Watering for Mature Trees
Once an arborvitae is established, typically after two years, the watering approach shifts to deep and infrequent applications. The standard rule is to provide the tree with the equivalent of one inch of water per week, either from rainfall or supplemental irrigation. This volume should be delivered in a single deep soaking session rather than several shallow sprinkles, which encourages the roots to grow deeper and wider.
Watering needs change throughout the year, requiring seasonal adjustments. During hot, dry summer months, especially when temperatures exceed 80 degrees, the frequency may need to increase to twice a week to compensate for increased evaporation. As temperatures drop in the fall, the frequency should be reduced. However, occasional deep watering is necessary before the ground freezes solid. This pre-winter hydration helps prevent desiccation, or winter burn, by ensuring the foliage has moisture reserves when frozen soil prevents water uptake.
Soaker hoses or drip irrigation systems placed directly at the base of the tree are effective application methods. These deliver water directly to the root zone without wetting the foliage, which helps prevent fungal issues. A layer of organic mulch, two to three inches deep, spread around the base but kept a few inches away from the trunk, conserves soil moisture and regulates temperature.
Identifying Signs of Water Imbalance
Diagnosing an arborvitae’s distress requires careful observation, as the visual symptoms of underwatering and overwatering can appear similar. Underwatering often manifests as the entire branch tips turning brown quickly, and the foliage becoming brittle. This browning is a sign that the tree is shutting down sections of its canopy to conserve moisture.
Overwatering often first causes the inner foliage near the trunk to yellow or turn brown before progressing outward. This occurs because excess water fills the air pockets in the soil, suffocating the roots and leading to root rot. A root system compromised by rot cannot transport water efficiently, causing the tree to display symptoms of drought even though the soil is saturated.
To determine the true soil condition, the most reliable method is the “finger test” or using a probe-style moisture meter. Push a finger or the meter six to eight inches deep into the soil, just outside the root ball. If the soil at this depth is completely dry, the tree needs water; if it is saturated and water can be squeezed from a handful of soil, overwatering is the problem.