Endangered Species Recovery Program

10. Jareds Peppergrass (Lepidium jaredii)

• Taxonomy
• Description
• Historical Distribution
• Current Distribution
• Life History and Habitat
• Reasons for Decline and Threats to Survival
• Conservation Efforts
• Conservation Strategy

Taxonomy.-- Lepidium jaredii was named by Brandegee (1894). Jared collected the type specimen "near Goodwin, San Luis Obispo County" (Brandegee 1894, p. 398). Hoover (1966) divided the species into two subspecies: Panoche peppergrass (L. jaredii ssp. album) and Carrizo peppergrass (L. jaredii ssp. jaredii). The type locality for Panoche peppergrass is "Arroyo Hondo wash north of Cantua Creek, Fresno County" (Hoover 1966, p. 345). The type locality for Carrizo peppergrass is by definition the same as that for the entire species. Although the most recent treatment of the genus (Rollins 1993) did not differentiate between the subspecies, California Native Plant Society (Skinner and Pavlik 1994) follows Hoovers taxonomy. Jareds peppergrass is in the mustard family.

Description.-- Jareds peppergrass (Figure 30) varies from 10 to 70 centimeters (4 to 28 inches) in height, and the stems may be branched. It has narrow leaves, which occasionally have a few teeth on the margins. Each plant has many tiny flowers, which are distributed along the upper portions of each branch. The flattened, egg-shaped fruits contain two seeds each (Munz and Keck 1959, Rollins 1993). Panoche peppergrass has white flowers and numerous branches, whereas Carrizo peppergrass has yellow flowers and few branches (Hoover 1937, 1966, Taylor et al. 1990).

Figure 30. Illustration of Jared's peppergrass.

Historical Distribution.-- Jareds peppergrass ranged from San Benito County south to San Luis Obispo County, with Panoche peppergrass occupying the northern portion of the species range (Figure 31). Locations mentioned in the literature prior to 1966 can be assigned to a subspecies only tentatively. Apparently, collections from Arroyo Hondo, Little Panoche Creek, Panoche Creek, Riverdale, south of Mendota, and 20 miles northeast of Corcoran (all in Fresno County), and between Panoche and Idria in San Benito County represent Panoche peppergrass (Hoover 1966, CDFG 1995, Taylor et al. 1990). Carrizo peppergrass was reported historically from the Carrizo Plain (including the type locality) and Estrella in San Luis Obispo County (Brandegee 1894, Hitchcock 1936, Twisselmann 1956, Hoover 1970).

Current Distribution.-- Currently, Panoche peppergrass is knon or presumed to be extant at approximately 15 occurrences. The majority of the sites, including Arroyo Hondo and Panoche Creek, are in the Ciervo-Panoche region of Fresno and San Benito Counties (CDFG 1995, Taylor et al. 1990, Beehler in litt. 1994). One or two sites may remain in southern Fresno County and another in the Orchard Peak area of San Luis Obispo County (Skinner and Pavlik 1994). Carrizo peppergrass remains extant on the Carrizo Plain Natural Area; the extensive colonies east and southeast of Soda Lake comprise a single metapopulation (Lewis 1997). Two other occurrences of Carrizo peppergrass have been discovered recently: Padrones Canyon in the eastern foothills of the Caliente Mountains in San Luis Obispo County, and the Devils Den area in Kern County (CDFG 1995, Taylor et al. 1990, Lewis 1997).

Figure 31. Distribution of Jared's peppergrass (Lepidium jaredii).

Life History and Habitat.-- Both subspecies of Jareds peppergrass are annuals. Germination requirements have not been reported for either taxon. Panoche peppergrass flowers from February to June and Carrizo peppergrass from March to May (Skinner and Pavlik 1994), but few plants bloom in dry years (Hoover 1937). In 1997, Carrizo peppergrass germinated in January (Lewis 1997). Both taxa have been reported from clay and from sandy soils. Panoche peppergrass occurs in dry stream beds, on alluvial fans, and on slopes. Associated species include a variety of grasses and forbs as well as the shrubs common saltbush, quailbush (Atriplex lentiformis), mulefat (Baccharis salicifolia), and scale-broom (Lepidospartum squamatum) (Hoover 1970, CDFG 1995, Taylor et al. 1990, Beehler in litt. 1994, Lewis in litt. 1994, Lewis 1997). Carrizo peppergrass may occur in association with spiny saltbush, Lost Hills saltbush, alkali daisy (Lasthenia ferrisiae), alkali peppergrass (Lepidium dictyotum), and a few other plant species in the low-lying, alkaline areas east and southeast of Soda Lake. However, in open areas without spiny saltbush Carrizo peppergrass often forms dense, single-species stands. Carrizo peppergrass grows in a slightly lower part of the Soda Lake basin than does Munzs tidy-tips. Soils in these lower areas remain saturated for extended periods and frequently have a black or whitish surface crust (Lewis 1997). In Padrones Canyon, Carrizo peppergrass grows on steep, south-facing slopes and on the ridgetop where isolated areas of alkaline soil occur. The primary associate in these areas is hillside daisy (Monolopia lanceolata) Lewis in litt. 1994, Lewis 1997). Both subspecies of Jareds peppergrass are found below 1,000 meters (3,300 feet) in elevation (CDFG 1995, Taylor et al. 1990, Beehler in litt. 1994, Lewis in litt. 1994, Lewis 1997).

Reasons for Decline and Threats to Survival.-- Panoche peppergrass populations have been subject to disturbance from sand and gravel quarrying. Trampling by cattle is a possible threat to populations of this subspecies (Skinner and Pavlik 1994, CDFG 1995, Taylor et al. 1990, Beehler in litt. 1994). Carrizo peppergrass does not seem to have declined. The only potential threats noted were sheep grazing at Devils Den and a minor possibility of cattle trampling on the Carrizo Plain (CDFG 1995, Lewis 1997).

Conservation Efforts.-- In 1988, Dean Taylor of BioSystems Analysis, Inc. and biologists from the Hollister Resource Area of USBLM began surveys for Panoche peppergrass in both historical locations and suitable habitats. After they discovered the Fresno and San Benito County populations, USBLM acquired several of the sites that were on private land and now protects them from mining (CDFG 1995, Taylor et al. 1990, Beehler in litt. 1994, D. Taylor pers. comm.). The Orchard Peak area is also on public land (USBLM 1993). Russ Lewis of USBLM conducted surveys for and mapped occurrences of Carrizo peppergrass in 1997 (Lewis 1997). The Carrizo Plain and Padrones Canyon populations of Carrizo peppergrass are in USBLMs Carrizo Plain Area of Critical Environmental Concern, which is managed primarily for the benefit of rare species (Lewis in litt. 1994, USBLM 1996a,b).

Conservation Strategy.-- To ensure the long-erm conservation of Jareds peppergrass, the strategy is to protect at least five distinct populations of each subspecies, representing the full geographic range of the species. However, the more populations, the greater the likelihood of long-term survival for the species. Therefore, as many populations as possible should be protected, even though more than five currently are known from public lands. 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. Protection from development and incompatible uses is equally important on both public and private lands. The most important task to ensure the survival of Jareds peppergrass is to exclude severe surface-disturbing activities such as mining and land conversion within occupied areas. Light grazing may continue where impacts have not been observed. However, population monitoring is necessary; if declining population trends are noted, management changes may be necessary. Field inventories for both subspecies also should be continued, particularly in wet years, to verify the status of historical populations and arrange for their protection. When surveys have been completed or at a maximum within 10 years of recovery plan approval, the status of Jareds peppergrass should be reevaluated.