Ask a Master Gardener: Consider heat-tolerant trees

BY BRIAN JERVIS Ask a Master Gardener
Saturday, October 06, 2012
10/06/12 at 4:43 AM

Q: I lost some young trees this summer. Now that fall is here I want to replant something more tolerant of the heat. Suggestions? - Minnie, Sand Springs.A:

After two summers of stunningly high temperatures and having lost trees due to heat and drought, it is no surprise that you want information about heat-tolerant plants. This topic was covered a few weeks ago at an OSU Horticulture Department plant materials conference.

A tree's ability to adapt to heat and drought depends on several factors. Water conservation is the most important factor; some mature trees may use up to 100 gallons of water daily during high heat and windy conditions. Heat-tolerant trees must have a deep and efficient root system to absorb available water. The leaves must also be modified to be water efficient. They do this by generally being smaller and in some cases having a thicker waxy coating. If water loss becomes critical, these trees may shed their leaves and regrow them when it rains.

Some of the trees and shrubs recommended for heat and drought tolerance include ones that are well known in our area and some that are not commonly planted. These recommendations came from the horticulturist from Sunshine Nursery in Clinton.

Examples of more heat-tolerant trees found in Tulsa landscapes are Arizona cypress, western soapberry, Chinese pistache, lacebark elm, Kentucky coffeetree, Chinese zelkova, desert willow, cedar elm and Caddo sugar maple. The Caddo maple is a native and is tolerant of heat, unlike most other maples. Also included in this group was a variety of bald cypress called "Frio River," said to be especially drought tolerant.

Trees and shrubs that are not commonly used in local landscapes but are felt to have drought and heat tolerance are Cedar of Lebanon, Taylor juniper, prairie elm, lacey oak, Texas red oak, miyabe maple, lacebark pine, bigtooth maple, netleaf oak, Cole's Select serviceberry, Blue Shadow fothergilla and Eve's Necklace (Texas sophora).

You will not likely find the uncommon species locally, but a call to the Sunshine Nursery in Clinton or a search online at nurseries such as Forest Farms likely will be helpful. Local nurseries will usually order any plants not in stock if there is demand.

It should be remembered that any new tree, however heat tolerant, will need regular watering for at least the first three years - the time it takes to get a self-sustaining root system in place.

If you have a garden-related question you would like the Master Gardeners to answer in a column, call 918-746-3701. Original Print Headline: Consider heat-tolerant trees

Garden tips

If you reseeded your fescue, start mowing with a sharp-bladed mower when it reaches a height of 3 inches. If weeds sprouted along with fescue, it is generally safe to use a postemergent herbicide such as Weed-B-Gon after the third new fescue mowing.
If your tree or shrub lost its leaves during the heat of summer, don't assume it is dead. If the twigs are still pliable (not brittle) and you can see any green when the bark is scraped off, it likely will survive.
Peonies, daylilies, and other spring-flowering perennials should be divided or planted now. There should be good selections at local nurseries now.

Associated Images:

Many gardeners are looking for new varieties of trees that will stand up to Oklahoma's heat. This desert willow, seen at Turkey Mountain, is a good example. BILL SEVIER/Courtesy