The amount of water a cedar tree uses is complex because the term “cedar” commonly refers to two distinct groups of conifers. True cedars belong to the genus Cedrus, including species like the Atlas and Deodar cedar, which are native to mountainous regions and are known for drought tolerance once established. In North America, many trees locally called cedar are “false cedars,” such as the Eastern Red Cedar (Juniperus virginiana) or Western Red Cedar (Thuja plicata). Understanding the water needs of these trees requires looking at their biology and the highly variable conditions in which they grow.
Cedar’s Baseline Water Requirements
The actual volume of water a mature cedar tree consumes daily is highly variable, but scientific studies offer a measurable range for the common false cedars. For a large, established Eastern Red Cedar with a 12-inch trunk diameter, the maximum water use can reach approximately 42 gallons per day under hot conditions with abundant soil moisture. Research indicates that the overall average daily water use for these trees is significantly lower, closer to 6 to 7 gallons per day across various sizes and conditions.
This water loss occurs through evapotranspiration, a process where water vapor is released from the dense, evergreen foliage into the atmosphere. Because cedars retain their needles year-round, they continue this water cycling even during winter, unlike deciduous trees. This evergreen nature contributes to a higher total water budget compared to many prairie species.
Environmental and Species Factors Affecting Water Use
A cedar tree’s water consumption deviates from the baseline based on several interacting environmental and biological factors. The species itself is a major determinant; for example, true cedars (Cedrus) are adapted to dry summers and often require less supplemental water than some false cedars, such as the Western Red Cedar (Thuja plicata), which prefers moist conditions. The tree’s size, measured by trunk diameter and canopy spread, directly correlates with its water use, as larger trees have more leaf area to transpire water.
Climatic conditions, specifically air temperature and wind exposure, significantly increase the rate of evapotranspiration, driving up the daily water demand. Hot, dry, and windy weather forces the tree to draw more moisture from the soil to cool itself and maintain its metabolic processes. The soil type also plays a significant role in water availability. Cedars thrive in well-drained soil and are highly sensitive to waterlogged conditions. Sandy soils drain rapidly, while heavy clay soils retain moisture longer but can lead to root problems if they stay saturated.
Effective Watering Techniques for Established Cedar Trees
Proper watering of an established cedar tree focuses on depth and reduced frequency to promote a strong, deep root system. Rather than watering lightly every day, a deep soaking every one to three weeks is generally recommended. This method ensures the water penetrates the soil 6 to 12 inches deep, encouraging roots to grow downward rather than remaining near the surface where moisture quickly evaporates.
The most effective application method involves using a soaker hose or drip system placed along the tree’s drip line (the outer edge of the canopy). These slow-release techniques allow the water to infiltrate the soil gradually without runoff or excessive evaporation. Watering in the early morning or late evening further minimizes water loss to evaporation, making the application more efficient. Applying a 2- to 4-inch layer of organic mulch around the base of the tree, keeping it away from the trunk, helps conserve soil moisture and regulate temperature.
Managing Cedar Trees During Drought Conditions
Established cedar trees are naturally resilient and possess adaptations that allow them to handle periods of prolonged water scarcity. Their thick, waxy needles and dense foliage help reduce moisture loss from the leaf surface. However, during extended regional droughts, supplemental watering is necessary to ensure survival, especially for trees that are less than two years old.
Signs of severe water stress include the browning of the inner needles, sparse foliage, and drooping branches. When water restrictions are in place, the focus should shift to survival watering, prioritizing a deep soaking once a month rather than routine maintenance. Applying water slowly to the root zone, using the deep-watering techniques, helps ensure the tree has a reserve to withstand continued dry periods. Fall watering is also important in dry years to prepare the evergreen foliage for the winter, a time when water can still be lost through transpiration.