Weekly Express-News Article

By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist

Saturday, June 14, 2008

“Second Choice Trees”

            There are some trees that have characteristics that make them desirable in certain situations, but are not first line choices when you are seeking a shade tree.  Here are some of those trees to consider. 

 

            In East Texas and across the middle South, hackberries can develop into a large, attractive tree.  In the San Antonio area they usually do not develop into a stately high value shade tree.  Hackberries usually stay relatively small and become twisted and gnarley.  The leaves are deciduous and when they drop the skeleton that is viable all winter is not appreciated like a red oak, cedar elm, or bur oak is. 

 

            The worst thing about hackberries is that they produce a huge quantity of seed that result in hackberry seedlings everywhere, especially everywhere that birds roost.  Birds love the seed carrying berry, and deposit the seeds in every rose bush, thicket and fence line where they sit.  The seeds are excreted by the birds, quickly germinate and then grow about six feet every season. 

 

            Families wanting to maximize bird numbers in a landscape should have a hackberry or two, but it usually works best if they are in the back of the yard.

 

            Hackberries provide large quantities of bird attracting berries in the summer and autumn.  In the spring, mulberries are a favorite source of berries.  This year, cedar waxwings were stripping the mulberries of fruit in April long before it was ripe.  Beyond its value as a wildlife food source, mulberries do not rate high on the list of top choice for a shade tree.  Like hackberries they spread everywhere.  The golden-colored root system is very opportunistic.  They spread widely from the tree and are especially fond of invading raised bed gardens. 

 

            Mulberries will grow to 35 feet tall and 50 feet wide.  They grow very fast, often 8 feet per year.  The wood is soft and prone to breakage. 

 

            Chinese tallow can grow to 35 feet tall, but they are usually shorter.  The crown grows to about 30 feet in diameter.  Tallow produces a large number of berries and rank after hackberry and about the same as mulberry in terms of spreading all over the neighborhood.  Enough birds eat the fruit to spread the seed, but Chinese tallow is not in the same league with hackberry and mulberry in terms of attracting birds. 

 

            What tallow does have is good autumn color.  The leaves can have purple red or orange leaves.  The berries are white and showy as well.  Tallow is short-lived and sensitive to both drought and cold. 

            Cottonwoods are welcome additions to streambeds as one travels West from San Antonio.  In well watered alluvial soils, they grow very large (75 feet) and are one of the few species that prosper.   In San Antonio in a typical landscape, however, cottonwood is probably not a good choice. On upland soils they seem to be short-lived due to drought, insects, and disease.   It can be very difficult and expensive to remove a dead 65 feet cottonwood. 

 

The only maples that seem suitable for a landscape in San Antonio are the Amur maple and the big tooth maple.  Neither of them gets tall enough to qualify as a large shade tree. 

 

            Silver maples are often sold by mail order.  In the North and East they make a reasonably desirable shade three, but in South Texas they die after a short life due to drought, and aversion to our alkaline soil.  Red maples and sugar maples are even more averse to our conditions.

 

            Acid loving pines such as the loblolly from East Texas last in plantings in our area until about the first drought they experience.  On some sites they will grow for about seven years and then succumb to the alkaline soil and dry conditions.  Afghan pines (Eldarica) are pines that originated from the Middle East and appeared to be well adapted, but they are very susceptible to a fungal dieback.  For conifers, stick to Arizona cypress, Japanese black pine, Italian stone pine, and Aleppo pine.