With seemingly no end to this prolonged heat wave, Texas Trees Foundation (TTF) is recommending that homeowners and business owners in the Greater Houston and the Gulf Coast regions water their trees immediately.

The Foundation has been receiving inquiries about what to do in response to temperatures remaining well above 100 degrees F for lo these many days — especially in urban centers, currently in the throes of urban heat, where pavement and less vegetation make it up to 10 degrees (F) hotter than the surrounding countryside.

In these times of extreme heat, trees should be given priority over other landscape plants, including lawns. A lawn left unwatered will naturally go dormant for the season and turn brown, but can turn green again after rain or watering.

A lawn is shallow. It can be re-established in a single season. A large tree cannot. Save the tree.

How to water your tree

• Do not water established trees at the trunk. Instead, water from the "dripline" — which is the edge of the tree’s branches and outward. The basic rule of thumb is to 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. Sprinklers are for lawns but not for 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: 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. This kind of "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.

Texas Trees Foundation’s Urban Forester Rachel McGregor reminds homeowners to follow water restrictions, but points out that "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."

Other techniques
Beyond the necessity of watering, keep these other tips in mind to help your trees survive:

• The best time for summer watering is in the morning or evening between the hours of 7 pm-8 am. Aavoid watering during the hottest part of the day, 10 am–6 pm, because water gets lost in evaporation.
• Remove grass and other plants which can compete within the soil root zone for available water. This water competition can be severe.
• Use mulch to conserve water and prevent weed competition. 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.

Do not use fertilizer or prune your tree during summer months. Both cause more stress. Fertilizers promote growth that the tree cannot sustain under unfavorable conditions and pruning off good leaves takes food away from an already stressed tree. The only pruning that should be allowed is to remove dead branches or any branches that pose a hazard.

Heat stress
Your trees will show signs if they are stressed from the heat:

• Wilted leaves are one of the early signs of stress on a tree during drought.
• Leaf scorching, when the edges of leaves or the space between a leaf’s veins turns brown

When a tree begins to exhibit signs of heat stress, irrigation should begin immediately to avoid long-term damage to the tree. Drought and high temperatures deliver a one-two punch to trees. Trees exhale moisture from their leaves in a process called transpiration. As temperatures climb, transpiration kicks into overdrive. During extreme heat, there isn’t enough water in the soil to replenish the water lost. When this happens, trees adopt survival strategies that can stress and weaken them.

The Texas Trees Foundation (TTF) is a non-profit tree planting organization dedicated to greening North Central Texas.