Prune by heading back as much of the new-ish growth as desired in April or May, after flowering. Further prune similarly if desired in November. New growth over the cool season will have time to develop flower buds for spring. Ceanothus are browsed by Deer. Think like you are a deer having a snack with your pruners. By mid-winter it is too late to prune or you will be removing the growth that would form the flower buds that will bloom in Spring (1). Not pruning immediately after flowers fade will result in branches with leaves, followed by stems with no leaves (where the flowers were) followed by leaves again. For dense shrubs, be sure to prune off the spent flower clusters. Ceanothus tend to die or not live long if given too much summer water. They are beautiful and very rewarding plants to grow, but not necessarily the easiest for new gardeners because of this (3). Older branches often do not react well to pruning, so it is better not to prune any branches greater than the diameter of a pencil (7). References