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. 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.