How to Grow & Care for California Lilac (Ceanothus)

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Ceanothus is a genus of over 50 shrubs and small trees. Its fragrant flowers are a pretty and unusual blue color. It is native to and grows wild in North West America.

This evergreen perennial bush, also known as the soap bush or buckbrush, is grown as an ornamental plant. It isn’t a lilac.


This is a shrub with history! One species of California lilac, Ceanothus americanus, was used as a substitute for tea in the late 1700s, during the American War of Independence. This species is commonly called New Jersey Tea. 

Following the Boston Tea Party, when a shipment of British tea was thrown overboard, and in the years that followed, New Jersey Tea served as a substitute tea product, although it does not contain caffeine.

Plant Facts

Scientific nameCeanothus
Common namesCalifornia lilac, soap bush, New Jersey Tea, Buckbrush, 
HeightUp to 10 feet (3 m)
WidthUp to 10 feet (3 m)
USDA Plant Hardiness ZoneUSDA zones 8 to 10
Native toNorth America
Blooming seasonSpring to Summer
Flower colorsBlue
Plant specific featuresNitrogen fixing shrub

How to Plant and Grow a California Lilac

You don’t often find a shrub that bears beautiful and often fragrant, blue flowers. So, if you can provide the growing conditions that suit the California lilac, it is an ideal choice.

Where to Plant

Ceanothus is an extremely adaptable evergreen shrub. You can plant it as a specimen plant against a wall or building, where its spectacular show of blue flowers will be fully appreciated. 

Or, it can be planted as a hedging plant, a privacy screen, or even as ground cover. California lilac can also be planted in a herbaceous border, where it will blend in with perennials, ornamentals, and other shrubs.

When to Plant

The best time to plant this shrub is between late fall and early winter. The newly planted California lilac will be able to establish a good root system with damp winter soil. This will enable the shrub to tolerate the forthcoming summer season.

If you are buying a nursery specimen, then this will already have an established root system and the shrub can be planted in the spring. 

California Lilac Care and Maintenance


The pH level isn’t too important for a California lilac, but neutral is ideal. Avoid planting where the soil is too wet, or too dry. Good drainage is important. 

The soil should be well-fertilized, and if your soil is heavy, then a good soil conditioner can be applied before planting. Use organic matter, such as well-rotted manure or leaf mold.


During the summer months, especially in the shrub’s early years, water regularly encourages good root growth. 

Thereafter, you only need to water a Ceanothus if it is unduly dry. Once established, this is a shrub considered to be fairly drought-tolerant.

When watering a California lilac, it is much more efficient to water it thoroughly and infrequently, rather than little and often. 

Intensive watering will soak the plant, and encourage the growth of its deep roots. Superficial watering will only encourage the shrub’s shallow roots.


Mostly, it isn’t necessary to provide any additional nutrients for a California lilac. But if you want to get the best growth from your shrub, you can apply an annual Spring feed. 

Use a universal, slow-release fertilizer at the base of the plant. Always follow the manufacturer’s instructions and recommendations when applying fertilizer and don’t apply more than the recommended amount. 

Mulch is a good idea as well, but don’t let the mulch touch the base of the plant, otherwise, you risk disease and rot.


This is a shrub that likes to be planted in a sunny position. Plant in full sun for the best results.

Pruning and Repotting

Ceanothus is a great shrub if you don’t want a plant that requires too much work! It actually thrives on neglect. It doesn’t like to be pruned hard, especially the evergreen varieties. 

If too much of the shrub is cut back, it probably won’t recover and will have to be replaced by a new plant.

To prune the Spring-flowering, evergreen bush, simply trim the side shoots and remove any dead wood once the flowering has finished. 

If you have a variety that flowers later in the summer, then you should delay pruning until the early spring. Never cut more than a third of the woody growth in one season.

A deciduous species of California lilac is a little more forgiving. Although it will take some time, it probably will recover from a hard pruning. 

You should prune this type in the spring, before it flowers, cutting back unwanted growth from the previous season.


If you have an evergreen California lilac, you can propagate it by taking cuttings from the current season’s growth. The best time to do this is in the late summer or early Autumn, once the flowering has finished. 

Make stem cuttings from growth that is starting to become woody. These are known as semi-ripe cuttings.

Deciduous Ceanothus can be propagated in the Spring, using the new, current season’s soft growth. These are known as softwood cuttings.

Pests and diseases

Watch out for deer – they love Ceanothus!  You may need to provide good deer-resistant fencing to protect your blue-flowered beauty.

As far as other pests and diseases are concerned, California lilac is not troubled significantly.

Occasionally the shrub will be damaged by scale insects and/or honey fungus.

Most often, however, diseased plants are the result of inappropriate planting conditions. If the soil is too wet and doesn’t drain sufficiently, then the shrub will rot. Growth will be stunted, and the shrub will die back. 

If the Ceanothus starts to show signs of yellowing leaves, this scorching is probably a sign of damage due to exposure to cold or wind. Consider the shrub’s planting position, and if possible, move it to a more sheltered location.

Yellowing leaves may also be attributed to a deficiency of certain nutrients in the soil. 

Temperature and Humidity

Keep this plant relatively dry, to avoid problems with fungal disease or rot. When watering, try to keep the water off the foliage as far as possible, and water the base rather than from overhead.

Depending upon your location, you can plant the California lilac on a south or west-facing wall to provide some shelter from cold winds and winter frosts.

Ceanothus is used with great effect in Mediterranean gardens.

If you are in a colder region, then there are Ceanothus cultivars available that are less sensitive, and likewise, some cultivars which are more heat tolerant than others.

An established California lilac is drought tolerant. 

Other Uses for California Lilac

One of the Ceanothus’ common names is soap bush. This name is derived from the former use of California lilac as a soap or shampoo agent. When mixed with water, foam is formed – like soap. 

The leaves were used medicinally, and also to make a tea substitute. California lilac isn’t listed as being toxic to humans, birds, or domestic animals.

This shrub is a good choice if you wish to attract bees and butterflies to your garden because the flowers are rich in nectar.

Types of Ceanothus You Can Grow

The genus is very large; in addition, there are also many cultivars that have been developed.

The choice is wide and includes varieties that are of different sizes. Whilst most have blue flowers, there are even some hybrids that have white or pink flowers. 

Only about 10 species of Ceanothus are grown in gardens, but of course, from these ten, many hybrids have been developed. In all, there are approximately 50 varieties from which to choose.

The majority of California lilac are evergreen, or at least semi-evergreen. These shrubs have deep green and glossy foliage which looks good all year long. This evergreen types flower in Spring and early Summer. 

Deciduous varieties have paler leaves and tend to flower later in the year, even into the Autumn. 

Ceanothus “Concha” has been given the Royal Horticultural Society (RHS) Award of Garden Merit. 

This evergreen hybrid has elegant arching branches and grows thickly at the base. It has an abundance of deep blue flowers in the Spring that are full of pollen.

Ceanothus “Blue Sapphire” has deep sapphire-blue clusters of blossom in the Spring and attractive arching branches. It rarely exceeds 5 feet (1.52 meters) in height or spread. 

There is a recent dwarf form of California lilac, which is called C.“Cool Blue”. This is a light-blue flowering plant that goes splendidly in a container. 

Place on a patio and when in bloom, it provides a spectacular floral display. You may even grow it in a hanging basket. 


There aren’t many shrubs that can compete with the California lilac for flower, color, and fragrance. Add to the pot, it’s easy to care for status, versatility, and multiple forms and you have a definite winner.

*image by Raydar/depositphotos

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