As Utah enters the peak heat of July, USU Extension experts are advising gardeners to prioritize deep irrigation and soil moisture monitoring to prevent water stress in trees and shrubs. The guidance comes as urban landscape irrigation accounts for 5-75% of annual municipal water use in the state.
Monitoring Soil Moisture
To maintain healthy landscapes, experts suggest that trees and shrubs should be watered less frequently but for longer periods than turfgrass. According to research from USU Extension, the goal is to ensure moisture reaches a depth of 18-20 inches to encourage deeper root growth and create more drought-tolerant plants.
Gardeners can determine if irrigation is necessary by using a soil moisture probe—or even a long metal rod or screwdriver—to check sub-surface levels. Alternatively, the 'feel method' provides a manual way to assess hydration. By squeezing a handful of soil taken from a depth of 4-8 inches, gardeners can check for moisture retention.
In sandy or loam soils, the soil is considered dry if it runs through the fingers without leaving a stain. In contrast, optimal moisture levels are reached when the soil forms a ball that leaves a thin layer of moisture and stain on the hands without any water running out of the ball during the squeeze.
Irrigation Methods and Rates
The amount of water required depends heavily on soil type and plant size. Sandy soils absorb water at approximately 2 inches per hour, followed by loam at 3/4 inch per hour, while clay soils have the slowest rate at 1/2 inch per hour. For smaller trees and shrubs with a trunk diameter of less than 4 inches, weekly irrigation of 1/2 to 1 inch via sprinkler systems may be necessary.
Drip irrigation is noted as an efficient method for these smaller plants, requiring between 5 and 5:50 gallons of water. However, drip irrigation is not considered appropriate for larger trees or turfgrass. For larger trees with a trunk diameter exceeding 4 inches, micro-sprinklers or bubblers that emit larger volumes are recommended to cover the wider root zone.
In southern Utah, these water requirements may be higher than in northern regions of the state. Additionally, newly planted trees and shrubs require more frequent watering until their root systems are fully established.
Signs of Water Stress
Identifying water stress early can prevent plant death. While wilting and leaf scorch are primary symptoms of dehydration, gardeners must be careful not to mistake over-watering for under-watering. Over-saturation can deprive roots of necessary oxygen, leading to browning leaves or even leaf drop.
For trees and shrubs located within turf areas, the heat of July and August may necessitate an extra deep watering one to three times per month via hand watering or lawn irrigation. To maximize efficiency, experts recommend grouping plants with similar irrigation needs into a single zone.
Summer Maintenance Tasks
Beyond irrigation, USU Extension provides seasonal guidance for various gardening tasks. While June tips focused on pruning, pest management, and fruit thinning to increase yields, July maintenance continues the focus on plant health through strategies like mulching and weed control.
Mulching around the base of trees and shrubs is specifically recommended to reduce competition for water and nutrients from weeds and grasses.
Local Extension Access
For residents seeking localized assistance, USU Extension maintains a significant presence across the state with 38 total locations. This network includes 28 county offices, five gardens and centers, and five Small Business Development Center offices.
Notable regional offices include those in Cache County, directed by Horticulture Professor Jaydee Gunnell, as well as offices in Beaver, Box Elder, Carbon, Davis, Duchesne, Emery, Garfield, Grand, Iron, Juab, Kane, Millard, Morgan, Piute, Rich, Salt Lake, San Juan, Sanpete, Sevier, and Summit counties.
