Clarkia speciosa ssp. immaculata
|Listed||December 15, 1994|
|Family||Onagraceae (Evening Primrose)|
|Description||Erect annual herb; bears flowers that are white or cream-colored at the base, shading into pink or red-lavender in the upper part.|
|Habitat||Soils derived from ancient marine terraces, in grasslands or openings in chaparral and oak woodlands.|
|Threats||Residential and commercial development; road maintenance activities; possibly grazing and competition with non-native grasses.|
Pismo clarkia (Clarkia speciosa ssp. immaculata ) is an erect annual herb with wiry, branched stems up to 20 in (50.8 cm) long. The petals are white or cream-colored at the base, shading into pink or red-lavender in the upper part and are 0.6-1.0 in (1.5-2.5 cm) long. This plant is distinguished from the sub-species speciosa by its larger flowers and the pattern of petal color. Pismo clarkia and the subspecies speciosa are geographically separated; the latter sub-species occurs north of San Luis Obispo from the Santa Lucia range to the Salinas River drainage.
Pismo clarkia is an annual herb that usually flowers from May through July, occasionally extending into September. It has been noted that plants do not necessarily appear in the same locations in consecutive years, suggesting that a soil seed bank may exist. Seeds are not known to have any specialized dispersal mechanism.
Pismo clarkia typically occurs in dry sandy soils derived from ancient marine terraces. Soils that support the plant occur in grasslands or openings in chaparral and oak woodlands at elevations below 600 ft (183 m).
This plant is very narrowly distributed on coastal marine terraces in a 10-15 mi (16.1-24.1 km) stretch of coast, from south of San Luis Obispo to Nipomo Mesa in western San Luis Obispo County.
About 16 occurrences have been recorded. Three of these are believed to be completely extirpated, five others have been partially destroyed by residential and golf course development. The four largest sites have been estimated to support 1,000-3,000 plants each; the smallest supports fewer than 50 plants.
At least three historical populations are believed to have been extirpated, and at least five others have been partially destroyed by housing or golf course developments or are located where developments have been approved. Extant populations are on private lands and are threatened by continuing residential and commercial development, road maintenance activities, and possibly grazing and competition with non-native grasses, including veldt grass. Mitigation efforts have frequently involved experimental attempts to establish populations in dedicated open space areas, but none of these attempts has created a viable, self-sustaining population.
Conservation and Recovery
A small amount of seed from two populations is being maintained for conservation purposes in the long-term seedbanking program at Rancho Santa Ana Botanic Garden. No other species-specific conservation efforts have been undertaken. Mitigation efforts for populations altered or destroyed by development have often involved attempts to establish new populations rather than avoidance or on-site preservation of existing populations. Attempts to reestablish populations on undeveloped portions of sites that will remain in open space are experimental. Although several of the population creation efforts are too recent to evaluate success, similar activities with other rare annual species have most often failed.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U. S. Fish and Wildlife Service. 1998. "Recovery Plan for Morro Shoulderband Snail and Four Plants from Western San Luis Obispo County, California." U. S. Fish and Wildlife Service, Portland, Oregon. 75 pp.