Week of September 3, 2001
By Calvin Finch, Conservation Director, San Antonio Water System, and Horticulturist
PECAN AS A SHADE TREE
A pecan tree can be a pretty spectacular shade tree. They are very large, reaching 100 ft. on good sites and have a classic spreading crown shape. As an added dividend you sometimes get a crop of delicious nuts.
Why then are most horticulturists, including me, not recommending pecans as a shade tree for San Antonio?
· Size is the first problem to consider. Pecans are just too large. If you plant one, your whole neighborhood is affected. Shade is great unless you want to garden or have a colorful lot, and most of us would rather pick our own shade trees.
· Pecans are prone to limb breakage. Pruning them frequently reduces the problem, but hiring a professional to prune a large pecan tree every five years is not an inexpensive proposition.
· Aphids love pecans and a pecan tree infested with aphids will result in honeydew (aphid excrement) all over everything under the tree. It is basically sugar water, but it is sticky and serves as a food source for sooty mold, which is ugly. Spraying pecans for aphids in an urban area is not practical. Spraying frightens the neighbors, is expensive and is not very effective.
· If you are a neatnik that likes a manicured look, pecans will drive you to distraction. They drop male flowers, honeydew, nuts, branches and leaves at various times during the year.
· Webworms attack pecans in the spring and again in the fall. All but the most radical nature lover think the webs and stripped areas are an eyesore. As in the case of aphids, it is impractical to spray webworms.
· Phylloxera is another insect pest that often affects pecans. The small insects attack the young leaves and stems to form garishly deformed leaves and stems. The effect is the stuff horror movies are made of.
· As for the nuts, between the squirrels, grackles, zinc shortages, pecan nut casebearers, drought, stink bugs and scab, total production of an urban tree is usually pretty small. The pecan is, I have to admit, a good wildlife tree.
If you still want a pecan for a shade tree after considering the issues, plant it on deep soils in full sun with 50 feet between it and other trees or the house.
For those of you that want a shade tree that will give you less problems, consider Texas red oak, live oak, Mexican white oak (Monterrey oak), cedar elm, Chinese pistache, Montezuma cypress, bur oak or chinkapin oak. None of them is the perfect shade tree but their list of potential problems is shorter than that of the pecan.
The autumn is the best time to plant shade trees. Dig the hole as deep as the container and two or three times as wide. Return the native soil to the planting hole, there is no advantage in adding compost or starter solutions. Mulch four inches over the root area and water when the soil dries to one inch under the mulch.
Do your fertilization in February when you spread one cup of slow release lawn fertilizer over the roots for every inch of tree diameter.