Black Dalea. Dalea frutescens, Legume Family: ( Fabaceae ), Black Dalea. Also Called: Black Indigobush, Sierra Negra, Black prairie clover, Black prairie-clover. We wish to thank Wikipedia, the free encyclopedia for some of the information on this page. We share images and information with Wikipedia. An evergreen perennial, fast growing, up to 3 feet high with a 5 feet spread. Most are about 3 - 4 feet high. Dalea frutescens height and small, blue-green leaves make it an attractive, easily established, low-maintenance groundcover for dry and arid sites. Dalea frutescens does not respond well to fertilizer and overwatering, especially in winter, although in our hottest summer weather supplemental water will help keep the foliage full. It is an excellent low maintenance groundcover, useful for erosion control on rocky slopes, or in areas of reflected heat. It is cold hardy to about 15 degrees F. An excellent Xeriscape plant. Quick Notes: Height: Up to about 3 feet tall and 3 - 5 feet wide. Flowers: Inflorescence with a short spike, 5 - 25 flowered. Flowers are small, pea flower like, purple/white. Flowering Time: Late January - Early March. Leaves: Pinnately compound, dark green with a fine texture. Found: The USDA claims it is native to the USA (NM, OK, TX). In Mexico it is native to Chihuahua, Coahuila, Nuevo Leon, & Zacatecas. Found throughout the Chihuahuan Desert. Hardiness: Said to be hardy to 0 �F. We don't think that is correct. We know of several people who had theirs freeze & die at 14 �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: 6.1 to 6.5 (mildly acidic) 6.6 to 7.5 (neutral) 7.6 to 7.8 (mildly alkaline) 7.9 to 8.5 (alkaline) 8.6 to 9.0 (strongly alkaline) Sun Exposure: Full Sun Partial Shade Elevation: 0 - 2,500 feet. Habitat: Rocky limestone hillsides in the throughout the Chihuahuan Desert. An ideal xeriscape landscape plant in Arizona. It grows in disturbed soil, roadways, sandy or gravelly areas. Miscellaneous: Flowering Photos Taken February 12, 2008. Glendale, Arizona Xeriscape Demonstration Garden.