Prepare to soon walk past a spot from which a soft, grape scent is escaping. If so, you will have experienced a signal that Texas mountain laurel trees (Sophora secundiflora) are in flower. Friendly discussions have not decided whether the scent smells like bubblegum, grape Kool-Aid, or soda. Whatever you decide, enjoy it because the blossoms fade fairly quickly, along with their fresh, sweet aroma.
This small tree is a native of the Texas Hill Country and northeastern Mexico. It is also known by several other names: mescal bean, sophora, and in Mexico, "frijolito." From rocky limestone soil, it is quite slow growing, eventually reaching 15 to 20 feet high with a spread of 8 to 10 feet. If you do not want to wait some years for a mature landscape tree, it is recommended to begin with a larger propagated one of at least 15-gallon size.
Evergreen leaves of Texas mountain laurel are dark green and leathery, producing a lush appearance year-round. In early spring, the sweet purple flowers emerge in cascading clusters much like wisteria. By mid-summer these give way to fuzzy, gray-tan seed pods. Inside the pods are rock-hard, bright scarlet seeds.
Both flowers and seeds of the Texas mountain laurel can be poisonous if eaten, especially to youngsters and pets. However, the risk is somewhat limited because pods and seed coats are extremely difficult to crack open. If ingested, they may pass completely through the digestive system intact. If concerned about the seeds, pods may be clipped off before they mature.
Early indigenous people valued the brilliant, lacquered seeds for ornamental and ceremonial uses. Today they are still used in Mexico and Central America by drilling and stringing the seeds to make bead-like jewelry.
Texas mountain laurel is cold hardy to 10 degrees Fahrenheit, is thornless, and one of the cleanest small trees around. It is therefore a good choice for patio and poolside garden displays. Plant in full or partial sun in an area with excellent drainage. It should be watered every two to four weeks during summer, and once monthly or less in winter.
Larvae of the pyralid moth may feed on the leaves, young twig growth, and immature seed pods. Control these caterpillars with applications of bacillus thuringiensis (commonly called ‘B.T.’), a widely available biological control agent. Otherwise the tree is not susceptible to other pests or disease.
Carpenter bees are attracted to the Texas mountain laurel flowers and densely crowd around them. Keep in mind that these large, black, very loud bees do not sting. Oblivious to your presence, they may be simply enjoying sweet sips of something that smells much like grape soda… or is it bubblegum?!
Mary Kidnocker is a University of Arizona Master Gardener who lives in the Green Valley area.
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