One of the most popular flowering trees is the Desert Museum Palo Verde (Cercidium hybrid 'Desert Museum'). Introduced in 1987 by the Arizona Sonora Desert Museum in Tucson, this hybrid is thornless, has a longer bloom period and larger flowers than the other species. It grows to 25 feet tall and wide and is hardy to 17 degrees F.
Desert Willows are another popular flowering tree (Chilopsis linearis). There are several varieties with different colored blooms that range from white and pink to deep burgundy and bi-color burgundy and white. They are deciduous and hardy to zero degrees F.
Texas Mountain Laurel (Sophora secundiflora) is evergreen, thornless and one of the cleanest small trees around. It produces large clusters of purple, wisteria-like flowers with a grape bubble gum fragrance in early spring. It grows very slowly to 15 feet tall and wide and is very cold-hardy, to at least 10 degrees F. A word of caution: the red-orange seeds are very poisonous.
Chaste Tree or Monk's Pepper Tree (Vitex angus-castus) has an interesting history. Monks in southern Europe and Asia, where the tree is native, reportedly used the seeds of the tree as a substitute for pepper. It allegedly has an effect on their libido. Fast forward to the 21st century and horsemen are using it as a herbal treatment for PPID (Pituitary Pars Intermedia Dysfunction or Equine Cushings Syndrome). The Vitex tree produces long, narrow spikes of fragrant purple flowers in the summer which attract bees, butterflies and hummingbirds. It easily handles our hot summers, and is deciduous in winter.