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Growing Ceanothus – California Lilac
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Ceanothus - Growing Guide

Growing Ceanothus – California Lilac

Few English gardens do not have at least one example of this splendid genus which originate from the pacific coast region and mainly in California. Here they live in impenetrable dense brushwood from the coast up to the mountain areas. Individual flowers are small and usually a shade of blue or white. Individually they are quite small, but they are produced in such a profusion of umbels, that they form a dense and showy spectacle over the whole plant. Most species and varieties are evergreen with small opposite or alternate leaves.

Ceanothus are perfectly hardy in all but extremes of climate. They however grow quickly, flower profusely and, therefore, have relatively short lives in our gardens. As they get older they can get leggy and scruffy and it may well then be time to start again with new young plants. The lifespan varies in different growing conditions. In higher rainfall areas they grow quicker and many live only 10 to 15 years. Where conditions are drier the life span may be extended.

These plants are excellent for the shrub border or for growing against the protection of a wall (eg C. ‘Concha’, C. ‘Cascade’ and C. ‘Puget Blue’). Low growing or prostrate forms can be used effectively as groundcover on a bank or in rock gardens (eg C. gloriosus ‘Emily Brown’, C. thyrisflorus var. repens).

Far and away the tallest growing ceanothus (and one of the most popular) is C. arboreus ‘Trewithen Blue’ which usually flowers twice a year and can grow to 20ft or so with a woody trunk. The plant will need staking throughout its life for support or it can be grown in a corner beside a wall.

Evergreen ceanothus require little pruning. Perhaps a little shaping of the tops of the plants to encourage more bushy new growth. Deciduous varieties definitely do need pruning or you will have few flowers and the plants may die quickly. C. ‘Gloire de Versailles’ and C. ‘Perle Rose’ should be pruned in March or April when last year’s new growth should be cut back to the base of the previous year’s wood to allow the whole plant to reshoot vigorously again. A good mulch after pruning will be a help.

Ceanothus grow best in full sun in a well-drained soil where they have some protection from cold winds. They are lime tolerant but may get chlorotic on chalky soils.

Not that many ceanothus will actually set viable seed with us. In hotter summers the seed seems to form but then drop before ripening. Semi-ripe evergreen cuttings taken in summer root easily on bottom heat (greenwood cuttings for deciduous forms). As your plants will be short lived and may get damaged in the occasional bad winter it is sensible to have a replacement crop of new plants in reserve.