Ask Mr. Smarty Plants

The Lady Bird Johnson Wildflower Center Native Plant Database has the following information: Desert-willow is a 15-40 ft., slender-twigged, small tree or large shrub, often with leaning, twisting trunk and open, spreading crown. Leaves are deciduous, willow-like, light green, both opposite and alternate, 4–12 inches long and 1/3 inch wide. The blossom is funnel-shaped, 1–1 1/2 inches long, spreading at the opening into 5 ruffled, petal-like lobes. The flower is dark pink or purple, often with white or yellow and purple streaks within the throat. The catalpa-like flowers are borne in terminal racemes. By early autumn, the violet-scented flowers, which appear after summer rains, are replaced by slender seedpods, 6–10 inches long, which remain dangling from the branches and serve to identify the tree after the flowers are gone.

Named for its resemblance to willows, this popular ornamental tree is actually related to catalpa trees, Yellowbells (Tecoma stans), and Trumpet vine (Campsis radicans). Its exotic-looking blooms, rapid growth, drought tolerance, and ease of maintenance have made it a sought-after plant within its range, which in nature is from south-central Texas south to Nuevo Leon and Zacatecas in Mexico and west all the way to southern California and Baja California. Adapted to desert washes, it does best with just enough water to keep it blooming and healthily green through the warm months. Many cultivars have been selected, with varying flower colors, leaf sizes, and amounts of seed pods. Mostly blooms heaviest May to June but will continue to bloom sporadically throughout the warm season after rains. Flower color ranges from solid white or muted pink to darker rose and purple, as well as two-toned combinations of those colors. Throat often yellow-tinged. Many cultivars available with varying flower colors.

Prune frequently during its first few years to encourage minimal or single trunks. Water occasionally during prolonged drought. Remove spent flowers and seed pods to encourage continued blooming. To encourage branching and blooming, cut back during winter dormancy by a third.