Thread-leaf Brodiaea [Brodiaea filifolia Wats.]

Thread-leaf Brodiaea [Brodiaea filifolia Wats.]

Listing CNPS List 1B R-E-D Code 3-3-3

State/Federal. Status -- CE/C1 AMARYLLIDACEAE Mar.-Jun.

Global Rank G2 State Rank S2.1

Distribution: San Diego County, Orange County, Los Angeles County, and Riverside County

Habitat: Vernally moist grasslands and the periphery of vernal pools are the typical locales where this species has been found. Species such as Sisyrinchium bellum and Nassella pulchra may grow nearby. The Darwin Drive (Diablo Clay) and El Camino Real (Altamont Clay) sites were largely devoid of shrubs and were situated in annual grasslands which may have been heavily grazed in the distant past. Aside from some soil indications that these areas were seasonally moist in the spring, there were few obvious indicators that any rare plants occurred at these locales.

Known Sites: One of the last known vigorous San Diego County populations was reported to be heavily impacted by a recent housing development in San Marcos which left a limited portion of the population in open space. The majority of the population was either graded or dug up for transplanting. It is very rare on a hillside west of Darwin Drive north of Crestmont Place near Guajome Regional Park. A small colony still is extant north of Palomar Airport Road and west of El Camino Real, despite partial grading of the site. Data Base reports are for southeast of the intersection of La Mirada Drive and Pacific Street in San Marcos; as well as nearby between San Marcos Boulevard, Pacific Street, and MacMahr Drive; a large population from approximately 0.7 mile north, northwest of Palomar College for the southeastern quarter of Section 4; also; another nearby locale approximately 0.6 mile south, southeast of Buena near Mission Road and the railroad tracks; approx. 2.5 miles north of the Carlsbad Raceway in the southwestern quarter of Section 31; just north of the Carlsbad Raceway in the northwestern quarter of Section 18; approximately 0.5 mile east, northeast of Landes Park near Vista; the claypits just north of Palomar Airport; near the southeastern corner of the junction of La Costa Avenue and Rancho Santa Fe Road; on the Carillo Ranch 2 km west of Lake San Marcos and south of the Carlsbad Raceway; on an east-facing slope adjacent to Elm Avenue and opposite the Wilshire Grammar School in Carlsbad. A 1936 herbarium specimen at SD is vaguely labeled as 4.5 miles south of Vista on [old] Highway 395, which might place it near North County Town Center and Bernardo Mountain. A sizeable population is still extant at the Nature Conservancy Preserve on the Mesa de Colorado and Mesa de Burro in western Riverside County. This corm is historically known from southern Riverside County near Vail Ranch, 2 miles south of Perris near Goetz Road, east of Perris in the San Jacinto Riverbed, in the hills around Arrowhead Hot Springs (i.e., 1 mile from the hotel on Arrowhead Springs Road) for San Bernardino County, and near the City of San Bernardino. Few of these historical locales are likely still extant. Confirmed reports are from near Glendora in Los Angeles County where it was found in 1988; a second site in Orange County was reported in 1989. Recent reports are from near Hemet in western Riverside County, east of California Street and north of the railroad tracks; as well as near Miller Mountain near the Santa Rosa Plateau.

Status: This corm is still substantially declining throughout its Southern California range. B. filifolia is systematically being eliminated by numerous, unrelated construction projects around the Palomar Airport and San Marcos areas. Populations near the City of Hemet may be similarly endangered. This species grows in open grasslands and sage scrub from a corm, and is unlikely to be noted except during its short flowering season, typically around May. As a result, surveys out of season are unlikely to discover its presence. Given the continued loss to populations despite California Endangered status, Thread-leaf Brodiaea is a strong candidate for Federally Endangered status. All populations should be fully protected.

Copyright May 1994 Craig H. Reiser.

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