Endangered Species Recovery Program
None federal or state. California Native Plant Society List 1A.
This annual plantflowers in May, June, and July after the soil dries. However, it grows only in years of above-average precipitation. Merced monardella is restricted to extremely sandy, subalkaline soils in low-lying areas bordering rivers. The native vegetation in these areas is grassland, but several collections were made in dry-farmed fields. The only associated species mentioned by collectors was naked buckwheat (Eriogonum nudum). Elevations at the historical sites range from approximately 15 to 80 m.
Merced monardella has square stems and opposite, lance-shaped leaves; both are gray-hairy and have a characteristic mint scent. Although the white flowers are small, the flower heads are showy because each one is surrounded by a circle of white bracts. Each flower produces four nutlets.
Historically, Merced monardella was collected from five individual sites that were clustered in two areas: near the Merced River south of Delhi in Merced County, and along the Tuolumne River near La Grange and Waterford in Stanislaus County. The most recent record of the species was from 1941. Merced monardella was not found at historical sites during recent surveys but may persist on private lands where access was denied.
Much of the suitable habitat for Merced monardella was converted to agriculture more than 50 years ago. The intensive, irrigated agriculture practiced today is incompatible with survival of this species, unlike the dry-land grain farming common in the past. Other activities that may have contributed to its decline include urban development and sand and gold extraction.
Subclass ASTERIDAE, Order LAMIALES, Family LAMIACEAE, Genus Monardella, Species leucocephala
Stebbins, J.C. 1993. Status survey of Monardella leucocephala (Lamiaceae) in the San Joaquin Valley, California. U.S. Fish and Wildlife Service, Sacramento, CA. 16 pp. + appendices; Jokerst, J.D. 1993. Monardella. Pp. 718-722 in The Jepson manual: higher plants of California (J.C. Hickman, ed.). University of California Press, Berkeley, 1400 pp.; Skinner, M.W., and B.M. Pavlik, eds. 1994. Inventory of rare and endangered vascular plants of California. Fifth edition. Spec. Publ. No. 1, California Native Plant Society, Sacramento, 338 pp.; Epling, C.C. 1925. Monograph of the genus Monardella. Annals of the Missouri Botanical Garden 12:1-106; Rarefind, California Natural Diversity Data Base, Sacramento.
10-15 mm wide
Merced monardella can be distinguished from the related species Sierra monardella (M. candicans) and coyote-mint (M. villosa) by the color of the stems, bracts, and flowers; microscopic differences in the flowers; and habitat.