How to grow Ceanothus

Ceanothus is an evergreen shrub with stunning blue flowers generally in late spring and early summer.

Ceanothus 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. As Ceanothus is easy to grow, I tag it green wheel barrow, as 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 in full sun, away from cold winds. Ceanothus originates from North America, particularly California. For this reason, it is also known as the 'California Lilac' which accounts for its dislike of cold, exposed gardens. Ceanothus is mainly H4 hardy defined as hardy in most of the UK from -10 to -5.

This means that Ceanothus is best planted in a sheltered spot in fully sun on well-drained soil, essentially mimicking the originating conditions. If your garden is exposed, consider growing the more hardy 'Autumnal Blue', which as the name suggests, flowers in the late summer and early autumn, illustrated below, or one of the deciduous types.

When Ceanothus is grown in a cold 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 cannot thrive. It's tricky to get going, but once established, Ceanothus is usually trouble free. Ceanothus is attractive to bees.

How long does Ceanothus live?

There are a number of answers to this question, but overall, Ceanothus is not viewed as a shrub with longevity. The closer the growing  conditions are to its native California, the longer the shrub will live, the wetter the conditions, the more short-lived, overall between 5-15 years. The shrub may continue to grow but look scruffy, and the tendency is to start again with a new shrub. It is worth bearing in mind, when choosing a spot to plant Ceanothus, that it may not be there forever.

The image below may seem a bit contrary to this view; the Ceanothus in the image has reached good maturity but it's fair to say it is benefitting from the warmth of growing against a wall, in a sheltered walled garden, so ideal conditions to extend its life span.

green  wheelbarrow medium difficulty to grow

Ceanothus is tagged Green wheelbarrow because planted in a sheltered spot it is trouble free which will be ideal in many areas, especially around the south of England and more sheltered gardens. It can be more difficult to grow in colder areas, especially around in gardens in the North of England. However, it can thrive with care taken to plant in a sheltered corner of the garden. True to say, in most of the south of the country, it will be easy to grow.

The same Ceanothus in full bloom and in close up showing the dozens of soft blue flowers

How to Prune Ceanothus

 As a general rule, it is unnecessary to prune Ceanothus.  If you find your Ceanothus is outgrowing its allotted space, Ceanothus can be pruned. The evergreen varieties (most) are pruning group 8, which recommends pruning after flowering. Most Ceanothus flower in late May and June and you are safe to prune from late June onwards.

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 may be 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 needs little or no attention and are an 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 (Blue blossom) 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 grow 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.  Ceanothus 'Blue Mound' is more compact, growing up to around 1.5 meters 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 vigorous and although Treweithen Blue is popular, it is 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. Its 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 H4 hardy and it needs to be planted in a sheltered spot on light well-drained soil.

If Ceanothus is not what you are looking for check out shrubs and bushesspring flowering shrubssummer flowering shrubsshrubs with autumn and winter interest; and evergreen shrubs.

Ceanothus x Pallidus 'Perle Rose'

Ceanothus x Pallidus 'Perle Rose'

This is an unusual form of Ceanothus, it is pink and deciduous.

Ceanothus 'Autumnal blue'

Ceanothus 'Autumnal blue'

This variety of Ceanothus flowers in the Autumn .

Updated 23.11.2021