Endangered Species Recovery Program
Taxonomy.-- The scientific name of this species, Eschscholzia rhombipetala, was published by Greene in 1885 (Abrams 1923). Jepson later reduced it to a subspecies of tufted poppy, assigning the name E. caespitosa var. rhombipetala (Munz and Keck 1959). Currently, the name E. rhombipetala is in use (Clark 1993).
Description.-- Diamond-petaled California poppy resembles Tejon poppy and Lemmons poppy in many respects. However, diamond-petaled California poppy may have erect or nodding buds, the flowers are small and yellow, and the bases of the leaves are fleshy (Hoover 1970, Clark 1993, Clark in litt. 1979). The fruits of diamond-petaled California poppy are conspicuous because they are 4 to 7 centimeters (1.5 to 3 inches) long, which may nearly equal the height of the plants (Hoover 1970). Diamond-petaled California poppy is distinguished from frying pans (E. lobbii), another poppy that occurs in the same general area, by leaf position and seed characteristics (Clark 1993).
Historical Distribution.-- Diamond-petaled California poppy was known historically from seven sites in the inner Coast Ranges (Figure 25): Corral Hollow in Alameda County; Antelope Valley near the town of Sites in Colusa County; Antioch and the hills south of Byron in Contra Costa County; the La Panza area and near Yeguas Creek in San Luis Obispo County; and Del Puerto Canyon in Stanislaus County (Hoover 1970, Clark 1993, CDFG 1995, Clark in litt. 1979, Bittman 1986b). Hoover (1970) mentioned that the species occurred in San Joaquin County, but no specimens remain to document his report (Skinner and Pavlik 1994).
Current Distribution.-- At least two extant populations of diamond-petaled California poppy are known. The first discovered in 1992; it was on a privately-owned portion of the northern Carrizo Plain in San Luis Obispo County. Although diamond-petaled California poppy was not present on the same site in 1995, it may reappear in favorable years. The second confirmed population is on Lawrence Livermore National Laboratory property in Alameda County, where it was discovered in 1997. It is believed to be the occurrence reported historically as Corral Hollow. Diamond-petaled California poppy may have been rediscovered at La Panza, but the identification is questionable. Another reported occurrence in San Luis Obispo County is sketchy (California Natural Diversity Data Base 1997). The other historical populations have not been observed since 1950 (Skinner and Pavlik 1994, Skinner et al. 1995).
Life History and Habitat.--The ecology of diamond-petaled California poppy has not been studied in detail. Flowering specimens were collected from March into early May. Conditions for germination, pollinators, seed dispersers, and demography are unknown. Most of the populations reported have been on hillsides, but community associations varied widely among the sites that have been described in detail. The Carrizo Plain site was open saltbush scrub interspersed with vernal pools; soil type was not reported. Associated species included spiny saltbush, several species of goldfields (Lasthenia species), Munzs tidy-tips, red brome, and other annuals (California Natural Diversity Data Base in litt. 1997). At Lawrence Livermore National Laboratory, diamond-petaled California poppy occurred on clay where an eroding bank merged with annual grassland. Other plants in the vicinity were the forbs wind poppy (Stylomecon heterophylla) and microseris (Microseris douglassii) and thegrasses pine bluegrass (Poa secunda), slender wild oats (Avena barbata), and red brome (California Natural Diversity Data Base in litt. 1997). Near La Panza, diamond-petaled California poppy was found on nearly barren areas of clay soils in association with San Benito thornmint (Acanthomintha obovata) and large-leaved filaree (Erodium macrophyllum) (Hoover 1970, Bittman 1986b). Clark (1993) indicated that diamond-petaled California poppy had been found in fallow fields. The historical sites were found at 9 to 1,000 meters (30 to 3,300 feet) in elevation (California Natural Diversity Data Base in litt. 1997).
Reasons for Decline and Threats to Survival.-- The reasons why diamond-petaled California poppy has not been seen at many historical localities are unknown. Natural land remains in most of the areas where it was collected historically, although some land in the vicinity of Yeguas Creek has been converted to agriculture and the La Panza area is subject to heavy grazing (CDFG 1995, Bittman 1986b). The Antioch area is growing rapidly and thus is subject to development pressure. Threats to extant populations are agricultural conversion on the northern Carrizo Plain and erosion at Lawrence Livermore National Laboratory.
Conservation Efforts.-- Concentrated surveys near historical locations led to the discovery of the Carrizo Plain and Livermore Laboratory populations. Searches in the La Panza area in 1991 revealed only Lemmons poppy (CDFG 1995). The diamond-petaled California poppy at Lawrence Livermore National Laboratory is being protected from disturbance by the Department of Energy (T. Kato pers. comm.).
Conservation Strategy.-- The conservation strategy for diamond-petaled California poppy is to protect the Lawrence Livermore Laboratory population and at least four other populations representing the full historic range of the species. Protected areas should be natural land in blocks of at least 65 hectares (160 acres) and should contain a minimum of 1,000 individuals to reduce the likelihood of extinction from intrinsic or random processes. Considering that suitable habitat remains at many of the historical sites, efforts to rediscover diamond-petaled California poppy should continue, particularly in years of above-average rainfall. Any other sites determined to have the appropriate community associations should also be surveyed. Possible sites include East Bay Regional Parks Black Diamond Mine, Los Vaqueros Watershed, and the Altamont Creek Watershed. If additional populations are discovered during surveys, threats must be determined on a site-by-site basis. Changes in site uses are not necessary unless impacts to the population are noted. Monitoring should be initiated as soon as occurrences are found. If additional populations are found but fewer than five populations can be protected, seed collection (Center for Plant Conservation 1991) and introduction to public lands will be necessary to ensure the continued existence of the species. The status of diamond-petaled California poppy should be reevaluated within 5 years of recovery plan approval or when surveys have been completed, whichever is less.