The whitethorn ceanothus is a densely branched evergreen shrub found in California, Nevada and southwest Oregon. Used for ground cover on slopes and steep banks, whitethorn ceanothus also provides barriers and cover for small mammals. Whitethorn ceanothus is a low-growing shrub that reaches 2 to 5 feet in height. Its branches terminate in sharp points, thus the name whitehorn. The flowers, which bloom from late spring to summer, are small and dense and range from 1 to 2 inches long. During the blooming season, the abundant white blooms appear to be covered in snow, hence its alternate name, snowbush. The whitethorn ceanothus is found growing along rocky slopes and prefers well-drained soil.
Prune the whitethorn ceanothus in the fall after the flowers and leaves have fallen off the shrub. This will ensure hardy and healthy growth the following season.
Cut back the top of the whitethorn ceanothus with pruning shears, and cut to the terminal bud, which is the main area of growth. Pinch back the growing tips and prune all lateral branches that are twisted and thin. The goal is to produce one strong and main stem leader.
Remove all diseased and broken branches by cutting off the entire stem. Remove all insect-infested branches to prevent infecting the bush. Whitehorn prefers pruning to its natural shape so make sure you don't over-prune the bush.
Prune to one central branch and cut off all weak stems on young whitehorns. This will free up essential nutrients to the rest of the bush. Remove all suckers, or stems growing up from the base of the plant.