Express-News Weekly Column

Saturday, June 9, 2001

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

SOME SMALL TREES THAT PERFORM WELL IN THE HEAT

Summer is close and it won’t be long until temperatures reach over 90 degrees F. every day. There are several selections of small trees that perform well in the heat in full sun. They grow fast and even bloom to provide important summer color when other plants want to hide from the heat.

Vitex or chaste tree reaches 25 feet on good soils, but most specimens in the San Antonio area are about 12 to 15 feet tall. It is a tree that is inclined to be about twice as wide as it is tall. Vitex is virtually insect and disease free. It is also a premiere xeriscape plant that does not seem to interest deer as a food source. The highway department uses vitex as a median tree; that’s how tough it is.  There are blue and white flowered versions. The blue is everywhere. To see a beautiful white colored specimen visit the San Antonio Botanical Gardens where one is growing next to the handicapped ramp going up towards the Carriage House.

            Vitex flowers look like candles about 4 inches tall. The hummingbirds and butterflies use them as a nectar source all summer long.

Desert willow is not a willow at all but was named “willow” because of its strap-like (willow-like) leaves and flexible-looking growth habit. It prospers in dry soils and is most noticeable in deep droughts like the ones in 1996 and 2000. I am not sure if it is noticeable because the orchid-like blooms are so spectacular or if it is because nothing else is blooming in the drought.

            ‘Bubba’ is a desert willow selection discovered by Paul Cox, Assistant Superintendent at the San Antonio Botanical Gardens and co-author of the book “Texas Trees: A Friendly Guide.” It has superior large purple blooms.

            Desert willow is not a disciplined grower. It is described as rangy by some critical observers, but when it is 100 degrees F. a 15-foot tall tree full of blooms on a dry lawn is a treasure.

Hummingbirds like desert willow and deer do not seem very interested in it.

Some of the crepe myrtles have started to bloom in San Antonio, others have been set back for a few weeks by powdery mildew, but be assured that crepe myrtles will provide a colorful show this summer and fall. Crepe myrtle is a xeriscape plant but not in the league of desert willow or vitex. To keep crepe myrtles blooming at peak levels during a droughty summer requires a deep watering every month. They will survive without irrigation but bloom better with limited watering.

Crepe myrtles are in the same category as hollies and nandinas in being important parts of most xeriscape landscapes. You can select a crepe myrtle to fit every size requirement in the landscape, from groundcover to low shrub, to large shrub to small tree. ‘Basham’s Party Pink’ grows to 40 feet on Highway 90 West and other sites in San Antonio. ‘Natchez,’ with its white flowers, has beautiful bark and reaches 20 feet tall.   ‘Muskogee’ is lavender and reaches 20 feet. ‘Comanche’ has red flowers and grows to 12 feet. To find a crepe myrtle that meets your needs visit the web site www.plantanswers.com or your favorite nursery. Most offer a list of the crepe myrtles along with the color of their blooms, growth habits, and bark characteristics. The best lists also describe the variety’s resistance to powdery mildew. The Indian named varieties are usually the best in that regard.

Crepe myrtles are prone towards multi-stemmed trees or shrubs. To train them to a single trunk (three trunks also is attractive) just remove the extra shoots as they emerge from the ground. Crepe myrtles bloom on new wood so can require more pruning than vitex or desert willow. If pruning is not your thing, make sure the plant is in full sun and the soil is good enough (fertilize in February, organic material over root system) to produce new wood each year without heavy pruning.