Lakeside Ceanothus [Ceanothus cyaneus Eastw.]

Lakeside Ceanothus [Ceanothus cyaneus Eastw.]

Listing CNPS List 1B R-E-D Code 3-2-2

State/Federal. Status -- /C2 RHAMNACEAE Apr.-Jun.

Global Rank G2 State Rank S2.2

Distribution: San Diego County; Baja California, Mexico

Habitat: Inland Mixed Chaparral, specifically in the region from Crest to the Lakeside foothills, includes the known habitat and range for the Lakeside Lilac. Hybrid shrubs seem to occur regularly in the latter area. Typically, this Ceanothus occurs in a dense, almost impenetrable chaparral with a mix of Chamise and other shrubs such as manzanita. This chaparral is taller growing and more mesic than other woody scrub areas in the region. At Crest the soil types are mapped as Acid Igneous rock land and Cieneba very rocky coarse sandy loam.

Known Sites: This large, showy shrub grows on slopes south of Interstate 8 near Chocolate Summit Road. It is common near Montana Serena Drive northwest of Crest, occurring over several hundred acres; this site and nearby outlying colonies (e.g., near Farrell Lane) may include a sizeable proportion of the total extant population for the species. Old herbarium specimens at the San Diego Natural History Museum include a regional cluster of sites at Oak Ridge Ranch on the east slope of El Cajon Mountain, as well as the southeast base and northeastern slope of this same mountain; also from a bluff between San Vicente Creek and the San Diego River, in the Barona Valley, on the Eckstein Ranch near Silverwood Wildlife Sanctuary, above the Philbrook Ranch in Lakeside, and 3 miles east of Poway on the road to Ramona. Several shrubs were observed on the ridgeline east of Mussey Grade near the gated entrance to San Vicente Reservoir. Old biological survey reports are from Section 33 along Wildcat Canyon Road near Lakeside, near Bullard Lane in Alpine, 0.25 mile northeast of the intersection of Wildcat Canyon Road and Muth Valley Road, south of Interstate 8 and adjacent to Flinn Springs Park, and near Mountain View Road northwest of the community of Harbison Canyon. Data Base reports are from the same region including El Cajon Mountain, along Cornelius Ranch Truck Trail northwest of Harbison Canyon, 0.75 mile west of Dehesa School, and on a north slope near the summit of Kimball Grade. Reports from Otay Mountain and McGinty Mountain are questionable. Shrubs of hybrid origin from east of San Vicente Reservoir have been examined which are closer to Ceanothus tomentosus with occasional black glands on the serrated leaf tips. An old report by McMinn from north of Pala mentions on the herbarium card the specimen's likely hybrid origin; intermediate towards Ceanothus leucodermis. A report by Raven 5 miles east of Torrey Pines may represent another hybrid occurrence.

One herbarium specimen at the San Diego Natural History Museum from Baja California was collected on the summit of a ridge 2 miles east of Cerro Coronel at 32 17' North. More material from this locale is needed to ascertain whether this represents more than a lone hybrid specimen.

Status: The primary population of Lakeside Ceanothus in the Crest region is relatively stable, but is becoming endangered owing to a number of encroaching residential projects. This distinct shrub should be considered for planting at regional county parks or other areas with suitable habitat near/within its historical range. Any reports from outside of the Crest or El Cajon Mountain region should be considered questionable due to possible intergeneric hybrids of other species which sometimes superficially resemble Ceanothus cyaneus. All substantial populations where this shrub is a dominant element should be protected. It is recommended that significant portions of smaller colonies or even, if possible, of habitat with scattered shrubs be placed into dedicated biological open space.

Copyright May 1994 Craig H. Reiser.

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