San Diego mesa mint is a California endangered plant species, which means that killing or possessing the plant is prohibited by the California Endangered Species Act (CESA). San Diego mesa mint is also listed as endangered under the federal Endangered Species Act. It is an aromatic, hairy annual herb in the mint family (Lamiaceae) restricted to San Diego County. San Diego mesa mint habitat is coastal terrace vernal pools occurring on gravelly loams called Redding soil. San Diego mesa mint has unique, bell-shaped purple flowers that typically bloom from March through June. It can self-fertilize, but produces more seeds when it is cross pollinated by its pollinators, the Eurasian honey bee and two anthophorid bees. Like most vernal pool species, San Diego mesa mint seed germination is dependent on the wet and dry cycles of vernal pools, saturated in the winter and dry for 6-8 months of the year. Individuals are typically 5-20 cm long and are often found growing alongside San Diego button-celery (Eryngium aristulatum var. parishii) and San Diego fairy shrimp (Branchinecta sandiegonensis).
San Diego mesa mint was once widespread in San Diego County, spanning from Del Mar Mesa to Kearny Mesa. Urbanization has fragmented and diminished San Diego mesa mint habitat. In addition to urbanization, threats to San Diego mesa mint include alteration of wetland hydrology, off-road vehicle activity, competition with invasive plant species, road widening projects, illegal dumping, and military activities. Drought, climate change, and fire control are also contributing to habitat alteration. Nonnative plants were identified as the most significant threat to San Diego mesa mint in 2010 because of the competition for space and resources they create.
Despite all of these threats, San Diego mesa mint has persisted since it was listed 1978. This is primarily due to conservation and restoration efforts that lead to the enhancement or creation of vernal pool complexes. In 1998, the Vernal Pools of Southern California Recovery Plan (PDF) was published in collaboration by the U.S. Fish and Wildlife Service and San Diego State University. This plan outlines recovery action for six vernal pool species listed as endangered, including San Diego mesa mint. Future efforts to restore and conserve vernal pools in California, including control of nonnative plants, are needed to preserve San Diego mesa mint.
CDFW has been involved in the following San Diego mesa mint studies and projects:
CDFW may issue permits for San Diego mesa mint pursuant to CESA, and you can learn more about California laws protecting San Diego mesa mint and other California native plants. Populations of San Diego mesa mint occur in CDFW's South Coast Region. More information on San Diego mesa mint is also available from the United States Fish and Wildlife Service Species Profile for San Diego mesa mint.