There are few shrubs that produce blue flowers in such quantity as the ceanothus. A shrub in full flower looks like a blue cloud.
There are over 50 species and a number of cultivars of this popular shrub. Some are deciduous but the majority evergreen. The leaves are usually small, toothed or indented and often shiny. They are, like the flowers, held in large quantities and give the shrub interest even when it is not in flower. The deciduous varieties tend to be looser in shape, and have larger leaves and looser clusters of flowers.
Not all are blue - there are a few white or pink varieties. Although coming from California most are completely hardy. They can be grown as a free standing bush, but they are often grown against walls, not so much for the warmth, but more because they look good in that position.
They will grow in most soils, but can look sickly on chalky ones. They can be left unpruned, but such plants can become leggy and then are difficult if not impossible to cut back to shape. A light trim after flowering keeps the plant compact, but pruning at this time can be more extensive if necessary.
Because they can be very vigorous growing and flowering shrubs they are sometimes short-lived and die suddenly. Don't worry, it will not be because you have done something wrong.