Summer-Holly (Comarostaphylis diversifolia (Parry) Greene ssp. diversifolia]
Listing CNPS List 1B R-E-D Code 2-2-2
State/Federal. Status -- /C2 ERICACEAE Apr.-Jun.
Global Rank G3T2 State S2.2
Distribution: San Diego County, Riverside County, and Orange County; Baja California, Mexico
Habitat: Southern Mixed Chaparral, usually on mesic north-facing slopes, is the preferred habitat of this large, showy shrub. Almost the entire population of Summer-Holly occurs west of Interstate 15. An odd distribution is sometimes seen with Summer-Holly near North City West, where isolated large shrubs are scattered across coastal chaparral. Quite a few such sites are known, yet rarely are more than a dozen specimens found in proximity to each other. In the larger populations elsewhere, the mature chaparral is extremely tall, dense, and luxuriant. Ceanothus verrucosus or Ceanothus tomentosus may be a co-dominant shrubs with well established Toyon and sparse Chamise at such sites.
Known Sites: A large population with hundreds of mature shrubs was recently found south of Encinitas Road and just northwest of Montura Road in San Marcos; most of the population was lost to residential grading. At least 1000 shrubs grow on the north slopes of Double Peak in San Marcos. A scattered, healthy population of shrubs occurs on the north-facing slope of Mount Whitney. A few were seen near Seal Rock in the Merriam Mountains and others occur west of Interstate 15 flanking Lawrence Welk Estates (one shrub seen east of the freeway near Champagne Boulevard). It is occasional on the steep north-facing slopes south of Questhaven Road. Limited populations are found in La Zanja Canyon, on the north-facing slopes of Escondido Creek near Buman Road, south of Shepherd Canyon in Mission Trails Regional Park, and on north-facing slopes near Del Mar Heights Road well east of Torrey Pines High School. Isolated shrubs were seen near Minnewawa Campground on the lower slopes of Otay Mountain. The shrub is scattered lightly at several locales in the San Marcos Hills west of Twin Oaks Valley Road in dense Scrub Oak Chaparral, and in Rancho Santa Fe east of El Nido Road on eroded east-facing slopes. More substantial populations are reported to the northeast of this valley. Other locales where Summer-Holly was seen in low numbers are a hillside near the upper reaches of Woodwardia Canyon on Otay Mountain, on the upper slopes south of Batiquitos Lagoon, and west of the Miramar Dump near the Interstate 805. A recent report is from the north-facing slopes south of Turner Reservoir near Moosa Canyon. Old biological survey reports note this species 0.5 mile northeast of Lake Hodges, in Carroll Canyon east of El Camino Memorial Park, near Fairbanks Ranch 0.5 mile north of La Zanja Canyon and 1 mile east of San Dieguito Valley, the Crest Canyon drainage near Del Mar, 1 mile north of Batiquitos Lagoon and 0.5 mile west of El Camino Real, west of Fairmont Avenue and Montezuma Road near San Diego State University, San Elijo Canyon southwest of Harmony Grove, east of Kaywood Drive in Escondido, southeast of the eastern terminus of Clairemont Mesa Boulevard, on the Sofa Ranch west of Twin Oak Valley, and in Hidden Meadows. Data Base reports show sites west of Rancho Bernardo and south of Lake Hodges, near Aldine Drive between Fairmont Avenue and El Cajon Boulevard, near Osuna Valley, on the north slope of San Miguel Mountain, on Soledad Mountain near La Jolla, the Escondido Creek Floodplain north of the San Dieguito Reservoir. It is reported by Roberts from Orange County near Seaview Park north of Niguel Hill, as well as in the Santa Ana Mountains on a single canyon slope above Highway 74 and west of the Lower San Juan Picnic Area. One shrub was seen on a hillside near Pacific Island Drive in Laguna Niguel. A Data Base report is from nearby at the Seaview Park area of Monarch Summit.
Ten specimens from Baja California are found at the San Diego Herbarium; south to 31 14' North where collected by Moran (SD 127485) southeast of Erendira.
Status: Summer-Holly is declining throughout its U.S. range. A few large populations occur within or near the City of San Marcos where they are threatened by residential development and warrent dedicated biological open space protection. Elsewhere the species is slowly but steadily declining. Substantial stands of Summer Holly should be protected; significant portions of isolated smaller stands should be protected within biological open space.
Copyright © May 1994 Craig H. Reiser.