White Thorn Acacia. Acacia constricta, Bean Family ( fabaceae ), White Thorn Acacia. Also called mescat acacia. We wish to thank Wikipedia, the free encyclopedia for some of the information on this page. We share images and information with Wikipedia. A large deciduous shrub or small multistemmed tree. The white thorns which give it its name are conspicuous, rigid and very sharp. Whitethorn acacia plants are long lived. Some plants in the Sonoran Desert are known to be more than 72 years old. In Arizona, it is found throughout the southern half of the state, extending southward throughout Sonora. Small disjunct populations have been collected from Baja California and Baja California Sur, the latter from the Magdalena Plain. In the Sonoran Desert, Acacia constricta is usually found in arroyos and washes, where it blooms in late spring (April-May), with a second round of blooms in July-October. The bloom depends on having a minimum amount of rain, followed by a period of warmth. The flowers offer no nectar and little pollen, and so tend to have few visitors. Quick Notes: Height: About 6 - 15 feet. Can reach 17+ feet. Flowers: Yellow puffballs, on a 2 to 3 inch long stalk, aromatic, biggest bloom in spring and early summer, then sporadic. Flowering Time: April to June. Again in July - October, if there is the traditional summer rain called a monsoon. Seed Pod: A slender, long pod, 2 - 5 inches long, dark brown, the pod sheath is constricted between the seeds. Flat elliptical seeds inside. Stems/Trunks: White thorns of varying length; typically 1/4 to 1in long and white; thorns are most obvious on young trees, fewer found on mature specimens; young stem growth has reddish color, turning brown to gray-brown and becoming furrowed and scaly. Leaves: The leaves are alternate, semi-evergreen, bipinnately compound, 2 to 4 inches long, with 4 to 6 pairs of major leaflets and 8 to 12 pairs of minor leaflets about ,1 inches long and 1/2 inch wide. They are green to gray - green in color. Found: Native to the Sonoran Deserts of California, the Southwestern United States, and northwestern Mexico. Hardiness: USDA Zone 8a: to -12.2 �C (10 �F) USDA Zone 8b: to -9.4 �C (15 �F) USDA Zone 9a: to -6.6 �C (20 �F) USDA Zone 9b: to -3.8 �C (25 �F) USDA Zone 10a: to -1.1 �C (30 �F) USDA Zone 10b: to 1.7 �C (35 �F) USDA Zone 11: above 4.5 �C (40 �F) Soil pH requirements: 6.6 to 7.5 (neutral) 7.6 to 7.8 (mildly alkaline) 7.9 to 8.5 (alkaline) Sun Exposure: Full Sun Elevation: 1,500 - 5,000 feet. Habitat: Dry, well-drained sandy, gravelly, and rocky soils on upper bajadas and moderate slopes, washes, flats, and canyons. in the lower mountains. A most attractive and abundant plant along roadsides, plains, and mesas. An ideal xeriscape landscape plant in Arizona. Miscellaneous: Flowering Photos Taken At Date Creek, Arizona. June 13, 2003.