Q: Can you suggest a quick-growing shade tree for our patio? The afternoon sun here is intense. — Neil Hansen, Tucson, Ariz.
A: Three small (20- to 30-foot-tall) Southwestern natives come to mind. All have graceful, rounded silhouettes and lovely flowers, and will grow quickly in anything but the nastiest caliche soils. Desert willow, Chilopsis linearis, is a multistemmed tree easily pruned to a single trunk. The leaves are (surprise!) willowlike. One of the longest blooming of all trees, desert willow has large tropical flowers — purple, pink, or white — that appear from spring through fall. It needs slightly more water than the next two choices. Southwestern sweet acacia, Acacia minuta, spreads a year-round canopy of lacy foliage in the freshest pale green. In spring, it becomes a bright yellow beacon as fragrant flowers cloak the thorny branches. Like desert willow, it is naturally multistemmed but is easily trimmed to a single trunk. Unlike the Australian acacias, sweet acacia is not allergenic. The most drought-tolerant patio tree is paloverde, Cercidium. Look for the new hybrids such as ‘Desert Museum’. Thornless, upright, and a speedy grower, it bears showy yellow flowers for several weeks in spring. In addition, paloverde trees are a good choice if you would like to attract birds to your garden.