Prostrate Spineflower [Chorizanthe procumbens Nutt.]

Prostrate Spineflower [Chorizanthe procumbens Nutt.]

Listing CNPS List 4 R-E-D Code 1-2-2

State/Federal. Status -- None POLYGONACEAE Apr.-Jun.

Global Rank G3? State Rank S3.1?

Distribution: San Diego County, Riverside County, Orange County, Los Angeles County, San Bernardino County, Ventura County; Baja California, Mexico

Habitat: Sandy openings in Chamise Chaparral are typical locales for the Prostrate Spineflower; however, it may also occur in sage scrub. It regularly occupies recently disturbed microhabitats such as the shoulders of dirt roads or areas of lightly brushed chaparral. At Rancho Cuca the soils utilized are Crouch rocky coarse sandy loam; Fallbrook sandy loams are mapped for the Riverview Road site; Cieneba-Fallbrook rocky sandy loams for the Gregory Canyon site.

Known Sites: The Prostrate Spineflower grows in chaparral openings at Poway near the proposed Midland Road extension (close to Ehman Road). It is locally common at Rancho Cuca near the eastern boundaries of this old Mexican land grant and on a chaparral hillside east of Sandia Creek. It is scattered in chaparral openings north of the freeway at Alpine and on a disturbed trail in chaparral near Riverview Road in Fallbrook; also noted on a sage scrub ridgeline west of Gregory Canyon near Pala. Other small populations examined include near Rocky Mountain Road well north of Jamul Butte, on Whale Peak near Ballena, within La Zanja Canyon, in Pamo Valley near Orosco Ridge, near Jamul Butte, both west and east of Olive Hill Road near Bonsall, on a coastal peak east of Interstate 15 and south of Poway Road, close to the Miramar Landfill in open Chamise Chaparral, south of Del Mar Heights Road and east of El Camino Real, in the chaparral south of Deerhorn Valley Road, and near Chocolate Summit Road west of Alpine. This spineflower is found as far north as a barren, rocky butte near Winchester in western Riverside County, but is apparently quite uncommon in this region. A second locale well to the south was noted near Colt Road and De Portola Road. This annual sometimes invades newly disturbed soils in habitats with no prior historical degradation. J. R. Reveal merges subspecies albiflora into synonymy with typical C. procumbens var. procumbens. The latter form is seen primarily along the immediate coast on sandy beach bluffs where it is now quite rare due to urbanization. It is still found at both the northern and southern extensions of Torrey Pines State Park; this coast form has distinctive greenish white (Torrey Pines) or deep yellow (Dana Point, Orange County) as opposed to white or cream tepals. Herbarium specimens for C. procumbens were examined from the east slope of El Cajon Mountain, Pauma Valley, Pacific Beach, Point Loma, northeast of San Vicente Creek, Carlsbad, 2.5 miles east of Encinitas on the road to Olivenhain, Hidden Glen, an old 1862 specimen from the National Ranch, Balboa Park, the Silver Strand, Harbison Canyon, Twin Oaks Valley and Gopher Canyon Road, east of Otay Lake, just north of Highline Road on Barber Mountain, northeast of Loveland Reservoir, in Del Mar, and by the U.S. Boundary Monument 238. The specimens mentioned near the beach are likely closer to the greenish-white flowered form. The Prostrate Spineflower is reported by Roberts from one site along the San Joaquin Corridor alignment in Orange County.

Thirteen specimens from Baja California are found at the San Diego Natural History Museum, south to a locale near 30 23' North where collected by Moran (SD 88855). The coastal form with a greenish coloration to the flowers is locally common on the beach bluffs south of Punta Mesquite near Plaza Santa Maria.

Status: Prostrate Spineflower is stable and apparently wide ranging in the "back country." Substantial potential habitat occurs in little explored chaparral in the San Pasqual region. Additional taxonomic work should be conducted focusing on a correlation between tepal color and geographic range; as well as genetic tests to more conclusively demonstrate that unique subspecies or varieties are not present. Field experience with live, flowering material indicates that plants growing near the beach may be distinctive and substantially rarer than the wide ranging interior form. Subtle differences may not be so readily apparent in pressed herbarium material. If distinctive, these beach forms should be protected. The interior form may be a pioneer species which historically did not have to compete with Eurasian grasses on recently disturbed sites. If this is true, higher disturbance factors coupled with the cumulative addition of aggressive non-native weeds might eventually bring about a reduction in available habitat on the urban periphery of coastal San Diego County.


Copyright May 1994 Craig H. Reiser.

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