Graceful Tarplant [Holocarpha virgata (Gray) Keck ssp. elongata Keck]

Graceful Tarplant [Holocarpha virgata (Gray) Keck ssp. elongata Keck]

List: CNPS List 4 R-E-D Code 1-2-3

State/Federal. Status -- None ASTERACEAE Aug.-Nov.

Global Rank G5T2T3 State Rank S2S3

Distribution: San Diego County, Riverside County, Orange County

Habitat: This plant frequents annual and perennial grasslands. Near the Miramar landfill it grows abundantly on Chesterton fine sandy loam among Eurasian grasses. Usually shrub cover is not well developed at Curving Tarweed sites, with a heavy incidence of invasive non-native grasses and herbs.

Known Sites: This species is locally common in the grasslands around Lake Henshaw, as well as about Otay Lake and nearby Proctor Valley. It is also found east of San Dieguito Reservoir near Aliso Canyon Road, west of the Miramar Landfill near Interstate 805 in mildly disturbed areas of the Pauma Valley, throughout Peñasquitos canyon west of Black Mountain Road, and in open terrain at upland locales around Cuyamaca Lake. It is scattered about eastern Otay Mesa and Otay Valley. Herbarium specimens examined were from El Cajon, Poway, La Mesa, and Jamacha Junction. Reports are from the Inaja Memorial in the Cuyamaca Mountains, Lakeside, and San Diego. It is locally abundant in the grasslands near Sweetwater Reservoir. Old biological survey reports note this species on a hill east of Murphy Canyon and north of Mission Gorge Road, on the north side of Carmel Valley near Interstate 5, near Fanita Drive in Santee, and at Rancho Monserate; also north of Tenaja Road and east of Squaw Mountain on the Santa Rosa Plateau. In Riverside County it grows southwest of Cherry Street in Temecula, and south of Polly Butte near Hemet in open grasslands. Lathrop and Thorne report it as locally abundant on the Santa Rosa Plateau.

There are no specimens of Graceful Tarplant at the herbarium of the San Diego Natural History Museum from Baja California.

Status: It is difficult to account for the limited range of this late-flowering species (the flowering period may account to some extent for limited herbarium collections). Where it occurs, usually in mildly disturbed or overgrazed grassland, it is often abundant, numbering in the thousands. As its habitat is usually situated on comparatively level, sparsely vegetated terrain, it is presumed to be substantially declining in San Diego County and western Riverside County due to urban development. Provisionally, substantial portions of all large populations should be protected. Additional collection data is needed to further assess the distribution and rarity of this species.

Copyright © May 1994 Craig H. Reiser.

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