Larrea divaricata or tridentata
The creosote bush is one of the most easily recognized and widespread of the desert shrubs. They range from the southwestern U.S. all the way into South America, from whence they apparently originally came during the late Pleistocene period. During the retreat of the North American ice sheet, they spread northward.
The original bush can live to be about a hundred years old, but it can produce "clones" of itself through a system whereby the inner stems die and new stems appear on the periphery. This produces a circular pattern of genetically-identical plants, with the rings expanding outward about a meter every 500 years. This "clone-family" can live a remarkably long time: the "King Clone", which is on BLM land near Victorville, CA, is estimated at 11,700 years old. If you consider the cloned shoots as part of the original plant, that makes it the oldest living thing on earth.
The small, resinous leaves help limit evapotranspiration, as well as making the leaves inedible to most desert dwellers, with the exception of a few insects. During rain, or in periods of high humidity, the plant gives off a strong, sweet odor. This odor may have inspired the common name, as the wood preservative called "creosote" doesn't come from this plant.
The plant produces yellow flowers, which are important to a number of species of bees, some of which time their emergence from underground burrows to coincide with flower production. Small, fuzzy balls also grow on the twigs; these break into half-moon shaped seeds. The hairs allow them to stick to clothing (and animal fur) for a short distance for transport. They also disperse easily on the wind.
Recent scientific studies have indicated that creosote bush, once used by Native Americans (Cahuilla, Pima, Papago) medicinally, may exhibit antimicrobial activity, may contain an antioxidant which appears to be helpful in treating malignant melanomas, and may also be useful as an anti-inflammatory.
M. Angeles, Verastegui, et al., "Antimicrobial Acticity of Extracts of Three Major Plants of the Chichuahuan Desert", Journal of Ethnopharmacology, 52, 1996, p. 175-177.
Bowers, Janice Emily (1993). Shrubs and Trees of the Southwest Deserts. Southwest Parks and Monuments Association, Tucson, AZ.
F. Brinker, "Larrea Tridentata (D.C.) colville (Chaparral or Creosote Bush)," British Journal of Phytotherapy, 3(1), 1993-1994, p. 10-30.
"Creosote bush", Microsoft Encarta Online Encyclopedia 2000, http://encarta.msn.com, 1997-2000, Microsoft Corporation.
C.R. Smart, et al., "An Interesting Observation on Nordihydroguaiaretic Acid (NSC-4291; NDGA) and a Patient with Malignant Melanoma - A Preliminary Report", Cancer Chemotherapy Reports, 53(2), April 1969, p. 147-151.
Stewart, Jon Mark (1993). Colorado Desert Wildflowers. Jon Stewart Photography, 73430 Indian Creek Way, Palm Desert, CA, 92260.
Stewart, Jon Mark (1998). Mojave Desert Wildflowers. Jon Stewart Photography, 8020 Dark Mesa Ave NW, Albuquerque, New Mexico, 87120