How to grow Ceanothus
A garden favourite, Ceanothus is a lovely, easy to grow evergreen shrub with stunning blue flowers which as the center image illustrates, looks fantastic when in full bloom, a beautiful blue cloud. The most common varieties have blue flowers in late spring and summer, although there are also white and pink blooming varieties. Ceanothus is easy to grow, and so is tagged green wheelbarrowas it requires little or no maintenance. The most important point when growing Ceanothus is to plant it in the right place at the start, which is a sheltered spot with sun, away from cold winds. Ceanothus originates from North America, particularly California, and so is also known as the 'California Lilac' which accounts for it's dislike of cold exposed gardens. Ceanothus are mainly ** hardy which means they do need a sheltered spot in the garden, and if your garden is on the chill side the best variety to grow is the more hardy 'Autumnal Blue', which as the name suggests flowers in the late summer and early autumn, illustrated below, or one of the discidous types.
Ceanothus will grow in almost any soil, but if rooted in a spot susceptible to cold winds or chill, the leaves can suffer from wind burn, which will cause them to turn discoloured, brown and the shrub will fail to thrive. It can be tricky to get going , but once established Ceanothus are usually trouble free.
Ceanothus are attractive to bees.
How to Prune Ceanothus
As a general rule is is not necessary to prune Ceanothus. If you find that a Ceanothus is outgrowing its allotted space, Ceanothus can be pruned. The evergreen varieties (which is most) are pruning group 8 which recommends pruning after flowering. There are some less common deciduous varieties, illustrated below left, which are pruning group 6 to be pruned in early spring. It is always good to mulch and feed after pruning. If there is a bad winter and the plant suffers from wind burn it maybe necessary to prune out the damaged area. At all times avoid cutting back into the old wood, or cutting back hard, as the shrub may not recover. Mostly Ceanothus need little or no attention and are a really attractive shrub to grow.
Good varieties of Ceanothus and planting combinations.
Picking a Ceanothus for your garden depends on the size you would like and hardiness. Very few of the evergreen varieties are fully hardy, (what is hardy?) listed as H4 is C. thyrisiflorus (Blueblossom) which is a low growing, spreading variety, evergreen, and with light blue flowers growing up to 1.5 metres but taller if grown against the shelter of a wall up to 2.5 meters. C. x delilianus 'Henri Desfossé' is a hardy variety although it is deciduous with dark blue flowers from July to September. Most other evergreen varieties are less reliably hardy and may require some winter protection.
Some Ceanothus do grow very large, up to 6 metres tall, with a spread of 8 meters, such as Trewithen Blue, which makes checking the plant label important to know the eventual size of the shrub Good strong blue varieties with the RHS garden merit award are 'Trewithen Blue' and 'Cascade.' C. ‘Autumnal Blue’ is attractive, upright growing to around 3 meters with sky blue flowers from mid summer to early Autumn, C. 'Blue Mound' is more compact growing up to around 1.5 meter in the right conditions. C. ‘Concha' is around 3 meters with darker blue flowers in late spring. There are lots to choose from around 55 varieties in all. Ceanothus can be quite vigorous and although Treweithen Blue is popular is grows large, more of a small tree than a shrub. All these named varieties have the RHS GMA .
Confusingly many are described as H4 which should be hardy to -10 but are also described as 'needing winter protection'. All I can offer is that in an exposed garden, which I have, Ceanothus fail to thrive and often the leaves are wind burnt and brown. Despite the hardy description, I would only grow the evergreen varieties in a sheltered warm spot preferably against a wall.
The early spring flowering varieties of Ceanothus look good with Clematis Montana illustrated in the image above right. Once planted in a sheltered spot away from chilly winds Ceanothus is trouble free and will reward with lovely blue flowers year after year. It's evergreen foliage is attractive small bright green leaves.
Ceanothus is also suitable and ideal for planting in coastal areas.
There are also a few deciduous varieties of Ceanothus, such as Ceanothus x Pallidus 'Perle Rose' illustrated below left, which have delicate, attractive pale pink flowers from mid summer to early Autumn. This variety is also ** hardy and it needs to be planted in a sheltered spot on light well drained soil.