Larrea tridentata

Larrea tridentata occurs in Mexico and the southern United States. It is unclear if a species of Larrea south of Mexico is Larrea tridentata (Carter 1997, Gentry 1993, Munz 1974, Powell 1998). If the two species are conspecific then the name L. divaricata has priority (Powell 1998).

Larrea tridentata is a common woody shrub in the southwest U.S. and Mexico. Its populations have increased in response to past land uses and management techniques. Many of these land uses, e.g. overgrazing by livestock, remain unchanged. Despite threats that include wild-collection for the medicinal trade, wildfire, drought, and development activities, it is unlikely that there will be a severe reduction in either abundance or range of this species.

Larrea tridentata occurs in the U.S. in Arizona, California, New Mexico, Nevada, Texas, and Utah. It also covers vast expanses along the northern boundary of Mexico from Baja California to Nuevo Leon, extending southward throughout Sonora, Chihuahua, Guanajuato, San Luis Potosi and Hidalgo (Mason and Mason 1987) and central America (Carter 1997, Stubbendieck et al. 1984).

Over 100. New Mexico: >20; Utah: >20; Arizona: >20; California: >20; Nevada: >20; Texas: >20.

Larrea tridentata is a dominant or co-dominant member of most plant communities in the Mojave, Sonoran, and Chihuahuan deserts. For instance, the creosotebush scrub phase covers 40 percent of the Chihuahuan Desert (Marshall 1995). It is estimated to occur on 35 to 46 million acres (14-18.4 million ha) in the southwest U.S. (Marshall 1995) Healthy populations can be seen at intervals while traveling along Interstate 10, Interstate 8, Interstate 25 south of Socorro, New Mexico, and Mexico Highway 2.

There is direct evidence of plant collecting from wild populations for the plant trade in the southwest United States and Mexico. Wildcrafted material is available in both local herb stores in New Mexico, Arizona, Utah, and California and from stores on the internet that are physically located from as far apart as Oregon to Massachusetts. Larrea is not cultivated for its commercial use as a medicinal plant, but the current demand for this plant by the commercial trade appears to be sustainable.

Wildfire is a threat to Larrea populations (Brown and Minnich 1986).

Larrea tridentata is also susceptible to severe drought during El Nino events. In dry years, Larrea tridentata undergoes severe moisture stress and subsequent defoliation. Older branches do not produce new foliage, but sprouting may occur. The cumulative result of an El Nino event can be a 60-80 percent stem dieback (Marshall 1995).

Urban and agricultural development and activities related to mineral, oil, and gas extraction have likely negatively impacted some populations. However, they are not seen as a significant threat in the near future due to the resilience of this species.

Desert tortoises dig their shelters under Larrea where its roots stabilize the soil-71% of desert tortoise burrows studied near San Bernadino, California were associated with it.