Ceanothus - Evergreen and Deciduoussubmitted on 7 July 2015
At this time of year I have the pleasure of seeing my neighbour's Ceanothus in full flower from my kitchen window. The mid-blue flowers really stand out against the glossy darkish-green leaves.
Ceanothus, also known as the Californian lilac, comes in both evergreen and deciduous varieties, and depending on the species flowers from late spring to early summer, or late summer to autumn.
It is happiest planted in fertile, well-drained soil in full sun, but doesn't like exposed windy conditions. Ceanothus is often best planted against a south-facing wall. Deciduous species and cultivars can tolerate more exposed situations.
Mulch your plant in late winter or spring with bulky organic matter, such as garden compost or well-rotted manure, but keep it away from the base of the shrub. Apply a general balanced fertiliser after pruning in spring at 70g per square metre (2oz per square yard) to promote new growth.
The pruning requirements depend on whether your plant is evergreen or deciduous. Routine pruning is not essential for evergreens and in fact they are best not pruned. If grown as a bush, promote branching by pinch-pruning the soft tips on young plants in spring. Shorten over-long branches by up to a half in midsummer after flowering using secateurs, but don't cut into older wood as the stumps may not regrow.
Late summer-flowering shrubs bear spring flowers on shoots that grew the previous summer and summer flowers on the current year's growth. Trim the previous season’s growth by one-third to a half in spring. (e.g. C. ‘Burkwoodii’, C. ‘Autumnal Blue’, )
Late-spring and early-summer flowering shrubs should be pruned after flowering, cutting back long, flowered shoots by one-third to a half. If more bushy growth is desired, trim lightly again in late summer. (e.g. C. thyrsiflorus ‘Skylark’, C. arboreus ‘Trewithen Blue’, C. dentatus, C. impressus)
Overgrown evergreen Ceanothus don't respond well to renovation pruning and if you have reached this stage you should consider replacing the plant.
Prune deciduous Ceanothus in early to mid-spring. These bear summer flowers on new shoots each year and routine pruning is usually carried out to generate many strong new shoots each year.
To develop the main framework of branches of free-standing shrubs in their first and second years, shorten all stems by up to two-thirds, cutting back to an outward-facing bud. In the second year, prune the previous season’s growth by up to two-thirds and shorten all side branches to 10-25cm (4-10in) from the main stems.
On established plants you should reduce the main, flowered stems by about a half. Cut back weaker sideshoots harder – by up to about two buds. Thin out unproductive or congested growth from the centre of the shrub. Deciduous Ceanothus generally respond well to hard pruning.
If you would like to try propogating your Ceanothus, you should take semi-ripe cuttings from an evergreen between mid-summer and autumn, while you should take softwood cuttings of deciduous varieties from late spring to mid-summer. They can be grown from seed, but germination is difficult.
Some recommended cultivars to look out for are:-
C. thyrsiflorus ‘Skylark’: Evergreen. A bushy shrub producing dark-blue flowers in late spring to early summer. Height 2m (6ft), spread 1.5 (5ft).
C. ‘Blue Mound’: Evergreen. A mound forming shrub, producing dark-blue flowers in late spring. Height 1.5m (5ft), spread 2m (6ft).
C. ‘Autumnal Blue’: Evergreen. An upright shrub bearing sky-blue flowers in late summer to autumn. Height and spread 3m (10ft).
C. × delileanus ‘Gloire de Versailles’: Deciduous. A bushy shrub, bearing pale-blue flowers from midsummer to autumn. Height and spread 1.5m (5ft).
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