As Utah faces intense sunlight, low humidity, and drying winds, landscape trees must be prioritized for irrigation to prevent loss during drought conditions. According to Utah State University Extension, trees are the most valuable plants in a landscape and should receive water priority over grass, which can more easily recover from long periods of drought.
Prioritizing Trees Over Grass
Effective tree maintenance requires moving away from frequent, shallow watering. Utah State University Extension research notes that short and frequent irrigation typically only wets the top few inches of soil, which encourages shallow root growth. This makes trees more vulnerable to wind, drought, and other environmental stressors.
Benefits of Deep Irrigation
Instead, homeowners should aim for slow and deep irrigation capable of reaching at least 10 to 20 inches into the soil. Because tree roots grow deeper than those of smaller plants, this depth is essential for long-term stability and health.
Optimal Water Delivery Methods
The method of water delivery also plays a critical role in tree survival. While overhead or sprinkler irrigation works well for shrubs and small plants, it is not ideal for trees. This is because the water output rate of overhead sprinklers often exceeds the soil's infiltration rate, leading to excessive runoff before the deep soil layers can be reached.
Recommended Emitters and Frequency
Experts recommend using point irrigation methods, such as a slow-running shower hose or drip irrigation with emitters. For best results, emitters with a flow rate between 1 and 8 gallons per hour should be used. During the dry summer months, it is considered essential to irrigate trees at least once a week.
Impact of Soil Composition
Soil composition significantly influences how often a tree must be watered. Trees planted in clay soil can withstand more extended periods of drought because clay has a slower infiltration rate and a higher water-holding potential. In contrast, trees growing in sandy or sandy loam soils require more frequent irrigation.
Identifying Your Soil Type
Homeowners can determine their soil type by wetting the garden soil and testing its texture between their fingers. If the soil feels sticky with minimal grit, it is classified as clay. If it feels very gritty, it is coarse sand. A texture that falls somewhere between gritty and sticky indicates sandy loam.
To remove the guesswork from watering, Utah State University Extension provides an irrigation calculator designed to quantify exactly how much water a tree needs. To use the tool, homeowners must input several specific variables, including the tree canopy diameter, which is calculated by averaging two perpendicular measurements of the shaded area under the leaves.
Users must also account for evapotranspiration—the amount of water lost from the soil through evaporation and transpiration. This data can be retrieved from the Utah Climate Center by selecting the closest weather station to view daily precipitation and evapotranspiration (ETo) totals for the previous seven days.
The irrigation calculator also assists in designing new irrigation setups by determining how many drip irrigation loops are necessary and what their circumference should be based on the canopy size. The tool recommends placing emitters 5 feet apart and ensuring each loop is also spaced 5 feet from adjacent loops.
For emitter selection, the university suggests using heads with a flow rate of 2 to 3 gallons per hour for clay soil, and 5 to 8 gallons per hour for sandy soil. For those using existing systems, such as soaker hoses or drip lines, the calculator can determine run times based on the number and flow rate of existing emitters, though users are cautioned that high-flow hoses may cause inaccurate calculations due to potential runoff.
Beyond irrigation, Utah's unique climate presents challenges for all woody plants. Selecting shrubs that can withstand the state's specific environmental stressors—such as intense sunlight and limited seasonal precipitation—is vital for a successful landscape. For those looking to identify specific species, the USU Tree Browser offers a database of 245 tree species found in Utah and the Intermountain West.
