Urban Heat Island
Texas Trees Foundation

With 75.7% of the state of Texas in a severe drought, and heat index values in Dallas at 105°F or higher, common questions the Texas Trees Foundation hears include "How much do I need to water my new and existing trees?" and "How should I care for my tree during a drought?"

Irrigation of trees during drought

During drought and water restrictions, trees should be given priority over other landscape plants, including lawns. A turfgrass lawn left unwatered will naturally go dormant for the season and turn brown but may turn green again after a rainfall or when irrigation is reintroduced. Even if reseeding or resodding is necessary, a lawn can often be re-established in a single season - a large tree cannot. Most importantly, during a drought, the goal of irrigation should be sustaining the tree, not watering for maximum growth. 

Instead of watering established trees at the trunk, irrigate from the dripline (edge of tree's branches) outward. Apply water in a circular band at least half as wide as distance from trunk to dripline.

Trees should be watered slowly and deeply. Spray irrigation (sprinklers) are great for lawns but not trees. Instead, use a bubbler, multiple drip emitter, or hand-held hose to deliver water to the tree's root zone. Water soil one to two feet deep each time. The simplest method of watering is to use a garden hose on a slow trickle and leave it in different zones within the dripline until you can easily insert a screwdriver into the soil. Deep watering encourages deep rooting; deep roots are best for a tree to survive drought. Irrigate established trees once every two weeks during growing season. 

"Please follow any water use restrictions in your area when watering your trees," says TTF's Urban Forester Rachel McGregor. "Trees provide an enormous asset to our landscape by reducing heating and cooling cost in our homes, cleaning the air we breathe, increasing mental and physical health, decreasing storm water runoff, and many other benefits."

Summer watering tips during drought:

• Water in the morning or evening from 7 p.m. - 8 a.m.
• Avoid watering during the hottest part of the day, 10 a.m. - 6 p.m., as more water will get lost in evaporation.
• Many plants, including turf grass, compete within the soil root zone for available water. Water competition can be severe. Remove grass and excess plant competition from around any tree to decrease water stress. 
• Use mulch to conserve water and prevent weed competition. Besides minimizing evaporation of soil moisture and limiting rainwater runoff, mulch protects the tree from mower and weed trimmer damage. Wood chips and shredded bark can be used for mulch. Cover the area about 2 to 3 inches deep; avoid the area next to the tree's trunk.
• Do not fertilize or prune during summer months. Fertilizers promote growth that the tree cannot sustain under unfavorable conditions and pruning off photosynthetic material (leaves) takes food away from an already stressed tree. Only remove dead or hazardous branches.

What is urban heat? 

Urban centers across the state exhibit higher temperatures than the surrounding countryside. 

Read more on urban heat: https://bit.ly/3ayGWa.

Resource link: https://bit.ly/3ayGWaj
Media Contact: Kristy Offenburger, (469) 859-1979, kristy@texastrees.org