The caterpillars of Erynnis pacuvius, the buckthorn duskywing, feed on this plant and other species of Ceanothus.
The larvae feed on various shrubs, deciduous trees and herbaceous plants, such as Calluna, Cytisus scoparius, Pteridium aquilinum, Rubus, Sea-buckthorn, willow and the European Larch.
Rhamnus californica, the California buckthorn or coffeeberry, a plant species native to California and southwestern Oregon
Rhamnus betulaefolia (Birchleaf Buckthorn) is a shrub or small tree of the Fabaceae family, the buckthorns.
It breeds in alpine shrub forests of Berberis, Rhamnus, Rhododendron, and Salix at 3,200–4,235 m altitude, descending in winter to slightly lower levels where it occurs in coniferous forests, primarily Picea.