Cedar trees, including true cedars (Cedrus species) and related conifers like Western Red Cedar (Thuja plicata), are often mistakenly viewed as high-water plants. Established trees are quite drought-tolerant, but all cedars require consistent moisture during their establishment phase, which can last for several years. Once their root systems are fully developed, their need for supplemental water decreases dramatically, making them low-maintenance trees in many climates. Understanding this distinction is the primary factor in clarifying the watering needs of these evergreens.
Water Requirements by Age
The watering regimen for a cedar tree changes significantly as it matures, with the first few years being the most demanding period. Newly planted cedar trees, generally considered to be in their first one to three years, require consistent and frequent watering to establish a new network of fine feeder roots. During the first week after planting, daily watering is often necessary, transitioning to every two to three days for the next few months.
The volume of water applied during this establishment phase is more important than the frequency, as the goal is to fully soak the original root ball and the surrounding soil. A general guideline is to apply 1 to 1.5 gallons of water per inch of the trunk’s diameter (caliper) each time you water. This deep soaking encourages the roots to grow downward and outward into the native soil.
Once a cedar is considered established—which can take between two to ten years—its water needs are drastically reduced. Established trees typically only require supplemental water during prolonged periods of heat or drought. A mature cedar may only need deep irrigation once every two to three weeks in the summer, focusing on the area between the trunk and the canopy’s drip line. The aim is to wet the top 6 to 12 inches of soil in this zone, ensuring the water reaches the deeper, permanent root system.
Assessing Soil Moisture and Drainage
Water management requires assessing the condition of the soil, as cedars are highly susceptible to root problems in poorly drained areas. The best way to check soil moisture is to use the “finger test” or a soil probe, pushing a finger 2 to 4 inches into the soil before watering. The soil should feel cool and moist, but not saturated or muddy; if you can form a ball of soil that drips water, watering should be postponed.
Cedar trees require a well-draining soil environment, as waterlogged conditions quickly deprive the roots of oxygen, leading to root rot. If your soil naturally holds too much water, you can improve drainage by incorporating organic material or planting the tree on a slight mound or slope to prevent water from pooling around the base.
Applying a 2 to 4-inch layer of organic mulch, such as wood chips or shredded bark, around the tree helps retain soil moisture and keep the soil temperature stable. Mulch reduces evaporation from the soil surface, meaning the tree needs less frequent watering. Keep the mulch several inches away from the trunk itself, forming a “mulch donut,” to prevent moisture buildup that can lead to trunk rot and pest infestation.
Signs of Water Stress
Diagnosing water stress in cedar trees can be challenging because the symptoms of overwatering and underwatering often look similar. A cedar suffering from a lack of water will typically show browning foliage, especially at the tips of the needles or branch ends, and the overall canopy may appear sparse. In a drought situation, the tree may intentionally sacrifice its older, inner foliage, a process called flagging, by turning it brown to reduce water loss and conserve resources for the new growth.
Conversely, overwatering causes damaging symptoms because the saturated soil suffocates the roots, preventing them from absorbing nutrients and water. Common signs of overwatering include yellowing or drooping foliage, which can mimic drought stress, and new growth that is discolored or fragile. The most definitive sign of chronic overwatering is the presence of fungal growth, like mushrooms, around the base of the tree or a foul, musty odor from the soil, which are indicators of root rot.
Managing Cedar Trees During Drought
During periods of prolonged drought or heatwaves, established cedar trees benefit from supplemental deep watering. This acute care is distinct from routine watering and focuses on delivering a large volume of water slowly to the deeper root zone. Techniques like using a soaker hose or drip irrigation system placed within the drip line of the tree are effective, as they minimize runoff and allow the water to penetrate the soil slowly over several hours.
The goal of drought watering is to soak the soil to a depth of 6 to 12 inches to reach the tree’s main feeder roots. To maximize absorption and reduce the amount lost to evaporation, the best time to apply water is in the early morning or late evening. This practice ensures the tree has a full supply of moisture to draw upon during the hottest part of the day.