Ceanothus, also known as the California lilac, is a fast-growing shrub with blue-purple flowers that bloom in either spring or summer, depending upon variety. Although there are varieties that do well all over the U.S., California contains the greatest variety of Ceanothus species. Ceanothus generally does not require pruning. Sometimes older plants will begin to look a bit unkempt and pruning at that time is appropriate. The best time to prune Ceanothus is at the end of the blooming period. Avoid pruning in late autumn as any new growth will die back when the weather turns cold.
Remove all dead flowers by pruning them off. Place them in a bag for disposal.
Prune the tips of each branch back to the desired length. Do not cut any stems that are larger than one-fourth inch in diameter.
Rake the debris in the gardening bed. Any plant materials that are left behind provide breeding areas for pests.