An award winning shrub that provides a dramatic impact in spring and summer, when the whole bush can be covered in a riot of colour. There are two main groups: evergreens which have small leaves and tight clusters of flowers and deciduous forms, which are hardier with larger leaves and looser clusters of flowers.
Family: Rhamnaceae (buckthorn family)
Botanical Name: Ceanothus
Common Names: Californian lilac
Foliage: Evergreen or deciduous green leaves.
Flowers: Dense flowering clusters in various shades of blue (a few varieties have pink or white flowers).
Flowering Period: Late spring to early summer (evergreens flower mainly in the spring, and deciduous forms flower in summer).
Soil: Well drained sandy or loamy soil. Avoid very damp or over dry conditions. Acid, alkaline or neutral pH.
Conditions: Full sun. South or west facing aspect, in a sheltered location.
Origin: Nearly all species come from California, hence the common term californian lilacs.
Hardiness: Most forms are reasonably hardy in the UK. Frost may cause die-back, so grow in a sheltered position.
Plant in a mild spot with good shelter from cold winds. Many varieties are not fully harding in the UK so are often trained against sunny walls. Ceanothus do not like being transplanted, so choose your planting spot wisely.
Most cultivars make excellent wall shrubs, although they are not climbers. There are also forms that are ideal for trailing over a fence or up a pergola.
Many forms are pollution resistant making them ideal city garden plants. Most are lime tolerant but they won't do well in poor shallow, chalky soil.
Water thoroughly during dry weather until well established. Mulch with organic matter in spring and add a general fertilizer.
Tie shoots and branches of evergreen kinds to wall supports.
Little or no pruning is required for evergreen varieties, however they can be pruned immediately after flowering to shape them and remove faded flower heads. Don't cut evergreens back too hard.
Deciduous varieties should be pruned in March by cutting flowered shoots to within 3in (8cm) of the previous year's growth.
Can be affected by scale insect and sooty mould can be a problem.
Take 3in (50cm) soft cuttings in july to August, and root in a well drained compost in a coldframe. Pot them on once rooted. Protect overwinter and plant out late the following spring.
There is a wide variety of types available in all shapes and forms, many of which have been granted awards by the Royal Horticultural Society.
C. 'A. T. Johnson' has rich blue spring flowers on arching stems, usually followed by a second flush in the autumn.
C. 'Autumnal Blue' hardy evergreen with rich blue flowers in late summer and autumn. Height to 6ft.
C. azureus, deciduous, half-hardy in UK, mid-green leaves and long fluffy panicles of small, deep blue flowers in late summer. Height to 12ft (4m).
C. 'Burkwoodii' hardy evergreen with deep blue flowers. Extended flowering season. Height to 6ft.
C. 'Cascade' provides a striking cascade of bright blue flowers in long clusters.
C. 'Delight' one of the hardiest forms, with dark blue flowers. Height to 10ft (3m).
Ceanothus x delileanus 'Topaze' is a deciduous late summer/autumn flowering form with mid-blue flowers. Less vigorous than 'Gloire de Versailles'. Height to 6ft.
C. dentatus early flowering with sky-blue flowers. Height to 5ft (1.5m).
C. 'Gloire de Versailles' is a deciduous form with
arching growth. Late summer/autumn flowering form with powder blue flowers. Height to 7ft (2.1m). Available from Thompson & Morgan.
C. impressus hardy evergreen with deep blue flowers in spring. Good wall shrub. Height to 5ft (1.5m), spread to 8ft (2.5m).
C. 'Marie Simon' is a pink flowering form. Height and spread to 5ft (1.5m). Available from Gardening Express.
C. rigidus has flowers in a dark and attractive shade of blue.
C. 'Southmead' has dark, glossy, leaves and velvety blue flowers. Height to 6.5ft (2m).
C. thyrsiflorus repens is a hardy evergreen prostrate shrub with mid-blue flowers in spring. Reasonably hardy. Height to 3ft (1m).