Express-News Weekly Column

Saturday, October 6, 2001

Submitted by Calvin Finch, Ph.D., Director of Conservation, SAWS, and Horticulturist

 

FALL IS BEST TIME TO PLANT SHADE TREES

 

            Autumn is the best time to plant shade trees. Shade makes life in South Texas more bearable. Shade trees on the lot add significantly to property values, reduce air conditioning cost and cut lawn irrigation needs.

Plant your trees this autumn and winter and they will have time to get established before the summer heat challenges survival.

It is not necessary to select a large tree to plant. Large specimens are expensive and hard to establish. Many times a small tree (1.5 to 2” in diameter) will grow faster than the larger specimen and pass it in size within a few years. If nothing else, digging the hole would motivate me to select a reasonable sized tree over the larger specimen.

            Select a place in the yard in full sun where the mature size of the tree will not interfere with utility wires, your house and other trees. Trees compete with each other; so, the closer they are planted, the more they affect each other. Thirty feet is a reasonable distance to have between other trees or your house. If you must plant under utility wires use small trees like Texas mountain laurel, loquat, desert willow, Mexican plum, yaupon holly, or the medium size crepe myrtles.

Dig the hole only as deep as the tree in the container and two or three times as wide as the root ball. Place the root ball in the hole and cover it up with the same soil you removed from the hole. Our native soil is not high quality material, but it is the soil in which the tree must survive. Adding organic material or soil treatments to the planting hole does not improve survivability or growth rate. In fact, a planting hole full of organic material can result in a dead tree.

            When a tree or shrub is newly planted it has a root system confined to the planting hole. If we have a soggy period of weather, the planting hole can fill with water and not drain in time to avoid drowning the roots. If the hole is filled with organic material the water penetrates especially easily and may not drain as quickly into the clay or caliche around it.

            Any organic material you have should be used for mulch. Pile it four inches deep over the root system but not against the trunk. Leave the trunk bare of mulch or soil. Bark can resist drying from the air, but it has not evolved to resist moist material. The mulch should look like a donut complete with hole in the middle. Leaves, shredded brush, bark, pecan shells and many other materials work well for mulch. A mulched tree may grow forty to fifty percent faster than a tree that has sod growing up to the trunk.

Water-in the tree well after planting. If temperatures are mild and rains frequent this autumn you may not have to water much until next summer. Feel under the mulch and when the soil dries to one inch apply enough water to wet the root ball, about five to fifteen gallons, depending on the size of the tree.

            A few weeks ago I described why pecans were generally not recommended for shade trees. They grow too large, have limb breakage and have numerous messy pests. Other problem trees include Arizona ash (short-lived, pests), tallow (freeze damage, seedlings), hackberry (pests, seedlings), silver maple (chlorosis, short-lived), chinaberry (short-lived), mulberry (short-lived, seedlings) and cottonwood (pests, short-lived).

            You may decide one of these trees is suitable for your yard because it has a special characteristic such as berries for birds or fall color; but, if you are looking for a long-lived, attractive, relatively easy to care for shade tree, they are not the best choice.

Recommended trees for San Antonio include live oak, Texas red oak, cedar elm, bur oak, chinkapin oak, Chinese pistache, Mexican sycamore, Mexican white oak, Montezuma cypress and lacey oak.