Ceanothus oliganthus is a species of shrub in the buckthorn family Rhamnaceae known by the common name hairy ceanothus. It is endemic to California, where it can be found in most of the coastal mountain ranges in dry habitat such as chaparral. This is a large, erect shrub approaching 3 meters in maximum height. The evergreen leaves are alternately arranged and may be up to 4 centimeters long. They are dark green on top, paler and hairy on the underside, and are edged with hairy teeth. The flower cluster is a cluster or series of clusters of blue or purple flowers. The fruit is a capsule which may be hairy or not, depending on variety. There are three recognized varieties with overlapping ranges. The variety of this species known as jimbrush (var. sorediatus) is sometimes treated as a separate species.
Plant Ceanothus oliganthus on rocky slopes, particular north facing ones in the southern, drier parts of its range. This plant is fairly sensitive to summer water. Best to avoid all direct summer water after it’s first year, though it will be happiest if it can stretch its roots out to a damper or irrigated area 10 feet away or so. This plant likes full sun but tolerates part shade.