Ceanothus (Californian Lilac)
Common name: Californian lilac
These attractive shrubs are native to North America, in particular the state of California, hence its common name. It is, however, very different to the popular(forms of Syringa). There are 50 species with both evergreen and deciduous forms among them. All ceanothus are sun lovers.
The evergreen varieties should be grown with the protection of a sheltered warm wall — they are not successful in open parts of the garden where they are subjected to cold winds. The deciduous forms are generally hardier and can be planted in a border, but even here the plants may be damaged in very cold areas.
Most ceanothus flower from mid to late spring, the blooms being varying shades of blue. Pink varieties are to be found among the later-flowering deciduous forms.
Popular species and varieties
If space is not a problem then the deep blue
Ceanothus arboreus is worth considering; it can produce a sizeable shrub. ‘Trewithin Blue’ is even better, noted for its richer colouring. It blooms in mid to late spring, and often produces a second flush in late summer
Most of the ceanothus seen in our gardens are named forms. Three to look out for are ‘Blue Cushion’, a very deep blue with a neat spreading habit; ‘Blue Mound’, well known for its dense clusters of bright bluein mid to late spring, and the deep blue ‘Cynthia Postan’, known for its free-flowering habit and good bushy form.
The majority grow into sizeable shrubs. There are some with a low-growing habit, including the vigorous Ceanothus thyrsiflorus var. repens (AGM) which reaches around 60-90cm (24-36in) in height.
In late spring and early summer it is covered with terminal clusters of light blue flowers. It’s an ideal plant for growing on a bank or over a low wall.
Among the deciduous ceanothus is ‘Gloire de Versailles’ (AGM). In mid-summer this produces large panicles of pale blue flowers — a very good subject for the border.
Soil type Light humus-rich soils in a sunny spot are ideal for these shrubs. Some can show signs of chlorosis in soils that are alkaline.
Planting This can be carried out during autumn or spring (the latter is preferable, as they will establish quicker as temperatures rise).
Maintenance The evergreens require little. The spring-flowering plants can be trimmed immediately after flowering, if necessary. Those that flower later should be trimmed in mid-spring, if required. The deciduous forms should be cut back hard in early spring to within 7cm (3in) of the old wood.
Propagation Take cuttings with a heel during mid-summer Insert them in a pot containing an equal quantity of peat and coarse sand. Overwinter them in a garden frame. Pot them on individually into 12cm (5 in) pots the following spring. The young plants should be ready for their permanent positions in autumn.
Pests and diseases Generally there are few problems. Scale insects, if found, can be treated with insecticide. Die-back of shoots is usually caused by frost damage.