Dallas Urban Heat Island Mitigation Study

Announced findings from the 2017 Dallas Urban Heat Island Effect report

July 13, 2022: Summer 2022 Watering Tips During Drought

Summer 2022 Watering Tips

Irrigation of trees during drought

In times of 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.

Also, instead of watering established trees at the trunk, irrigate from the dripline (the edge of the tree’s branches) outward. As a basic rule of thumb, apply water in a circular band that’s at least half as wide as the distance from the trunk to the dripline.

Trees prefer to be watered slowly and deeply. Spray irrigation (sprinklers) are great for lawns but not for watering trees. Instead, use a bubbler, multiple drip emitters, or a hand-held hose to deliver water to the tree’s root zone. Water the soil to one to two feet deep each time you water and let the surface dry between waterings. The simplest method of watering is to turn your 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. Remember, deep watering encourages deep rooting – and deep roots are the best way for a tree to survive a drought. Irrigate established trees once every two weeks during the growing season.

”Please follow any water use restrictions you have in your area when watering your trees,“ says Texas Trees Foundation’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 our mental and physical health, decreasing storm water runoff, and many other benefits.”

How can homeowners and business owners mitigate urban heat and help trees survive drought?

  • The best time for summer watering is in the morning or evening from 7 p.m. to 8 a.m.
  • Most importantly, 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, can compete within the soil root zone for available water. This 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 Mulch is any tree’s best friend. Besides minimizing evaporation of soil moisture and limiting rainwater runoff, mulch also protects the tree from mower and weed trimmer damage. Wood chips and shredded bark can be used for mulch. Cover the area with mulch about 2 to 3 inches deep, taking care to avoid the area next to the tree’s trunk.
  • Using fertilizer or pruning your tree during summer months can cause more stress to your tree. 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. The only pruning that should be done at this time is to remove dead branches or any branches that pose a hazard.


July 2022: Summer Watering Tips (.PDF)

Texas Trees Foundation announced findings from the 2017 Dallas Urban Heat Island Effect report, a year-long study of the impacts and implications of air temperatures at the neighborhood level. Most notable among them: Dallas is heating up faster than every city in the country except for Phoenix.

The Dallas Urban Heat Island study and ensuing report was completed by Dr. Brian Stone, Professor, School of City and Regional Planning, Georgia Institute of Technology, and author of The City and the Coming Climate – Climate Change in the Places We Live. The report determined, “Cities do not cause heat waves – they amplify them. Human activities on climate at the city/regional scale, accounting for both land surface changes and emissions of greenhouses gases, may be twice as great as the impacts of greenhouse gases alone.” Dallas, with 35 percent impervious surface (i.e., rooftops, parking lots, highways, etc.), is hot – and getting hotter. Urban areas retain heat in the buildings and pavement and are up to 15°F warmer than rural areas where trees and open space are more prevalent.

The ramifications of urban heat adversely affect public health, longevity of infrastructure, public opinion, and our economy. With rising temperatures come higher costs for energy and a threat to our energy supply.

Key findings from the study include:

  • Sustained High Temps. Hottest areas of Dallas measured an AVERAGE HIGH of 101°F and LOW of nearly 80°F for five full months of the year.
  • Heat Kills. Heat-related deaths peaked at 52 in 2011 in Dallas County. Heat-related deaths in the United States account for more deaths annually than all other natural disasters combined.
  • Trees Cool. Tree planting in the hottest areas with high density residential was found to reduce deaths by more than 20 percent by merely dropping temperature alone.

Janette Monear, Texas Trees’ chief executive officer, remarked, “Our foundation is focused on making spaces cooler, greener and cleaner, and data has long affirmed that trees are vital to achieve this laudable and critical goal. The study we have released today is a wake-up call for all of us who call Dallas and North Texas home: We must act now to mitigate the urban heat island effect for the sake of our health, the economy and viability of our community. North Texas is seeing unprecedented growth, and with growth comes new buildings, roads and parking lots. It’s imperative that we come together to balance the grey with the green to ensure North Texas is a desirable place to live and work.”

Corporate partners like Alliance Data, Wells Fargo, and American Forests who funded the study understand the ramifications of urban heat to their bottom line.

“With a dual perspective from my seat as Chairman of the Board for Children’s Health System of Texas, and as the leader of a Fortune 500 company headquartered in North Texas, the economic impact of the rising temperatures in Dallas has never been more at risk,” said Ed Heffernan, President and Chief Executive Officer, Alliance Data. “We know from our partnership with Texas Trees Foundation and data from the Urban Heat Island study that health is directly impacted when temperatures increase and air quality declines. Childhood asthma rates are at an all-time high, with nearly 10 percent of all Dallas children suffering from asthma. We care about the health and well-being of our associates, which is why Alliance Data funded this study and why we’re committed to standing with Texas Trees Foundation to make a difference.”

Texas Trees Foundation’s study offers cost-effective solutions to making Dallas one of the coolest cities in the country. Tree planting in concert with reflective pavement and roofing materials are the most cost-effective ways to manage the urban heat island effect.

Together with area municipalities, corporate leaders and non-profit partners, Texas Trees Foundation strategically plants trees in parks, school yards, along streets and other public rights-of-way and provides urban forestry consultation services to create a better quality of life throughout North Texas.