|Listed||September 28, 1987|
|Description||Prostrate annual with leaves in a basal rosette and a slender flower stalk.|
|Habitat||Alluvial fan scrub.|
|Threats||Limited numbers; urbanization; sand and gravel mining.|
Slender-horned spineflower (Dodecahema leptoceras ) is a prostrate annual with leaves in a basal rosette. From the middle of the rosette, which may be up to 4.5 in (11.4 cm) in diameter, the plant sends up a flower stalk 6.8 in (17.3 cm) high. Three-lobed horned bracts occur at nodes on the flower stalk. Leaves and bracts turn bright red with age. Flowers are compound, consisting of three or more tiny inconspicuous blossoms in a ring. The species has also been known as Centrostegia leptoceras.
Slender-horned spineflower is found in sandy-silty alluvial soils. These soils are deposited in fans where streams emerge from ravines onto a flood-plain. The alluvial fans support a variety of scrub plants that receive little natural disturbance other than occasional flooding. Flooding plays a crucial role in maintaining fan scrub. Without it, scrub is gradually overshadowed and displaced by woody growth. Associated scrub plants are old California juniper, mountain mahogany, and Yerba Santa. Habitat elevation ranges from 500 to 2,000 ft (152 to 610 m).
This species, formerly more widespread, is endemic to the floodplain benches and terraces of Los Angeles, San Bernardino, and Riverside counties, California. Populations in Los Angeles County have been eliminated by urbanization. The range of slender-horned spineflower overlaps that of the federally endangered Santa Ana woolly-star (Eriastrum densifolium ).
The plant is currently found in small populations from five localities in San Bernardino and Riverside counties. These populations are adjacent to Lytle Creek, Santa Ana River, Temescal Creek, San Jacinto River, and Bautista Creek. The area of remaining habitat totals less than 10 acres (4 hectares).
Much of the naturally occurring alluvial fan scrub of the Los Angeles Basin has been displaced by the explosive growth of the Los Angeles metropolitan area. Documented sites in San Bernardino and Riverside counties have been lost to residential development or destroyed by sand and gravel mining.
Conservation and Recovery
Several surviving populations occur on lands managed by the Bureau of Land Management (BLM), which oversees leasing of mineral rights. The BLM has prepared a management plan that seeks to balance conservation of fan scrub habitat with current and proposed mining activities. BLM jurisdiction over these lands, however, may soon be ceded to state and county authorities, an action that would undercut federal protection. The California Fish and Game Commission lists the spineflower as endangered, protecting the plant from collection, but not from habitat destruction.
The U. S. Army Corps of Engineers has proposed new flood control projects for the upper Santa Ana River Canyon and Lytle Creek that would probably result in relaxation of zoning restrictions that now apply in San Bernardino County. Further development on the floodplain would almost certainly eradicate the last remnants of alluvial fan scrub habitat. Before proceeding with these projects, the Corps is required to consult with the U. S. Fish and Wildlife Service under requirements of the Endangered Species Act. Consultations will consider the welfare of the slender-horned spineflower and remaining portions of its habitat.
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
Krantz, T. 1984. "A Review of the Endangered Status of the Slender-Horned Spineflower Centrostegia leptoceras Gray and the Santa Ana River Woolly Star Eriastrum densifolium ssp. sanctorum (Mlkn.) Mason." Report. Bio-Tech Planning Consultants, Big Bear Lake, California.
U. S. Fish and Wildlife Service. 1987. "Determination of Endangered Status for Eriastrum densifolium sanctorum (Santa Ana River Woolly-star). Federal Register 52 (187): 36265-70.