California Lilac (Ceanothus) – The Complete Guide

No, this is not a species of lilac (Syringa), even though its bushy panicle flowers look quite similar.

However, the California lilac can enrich your garden in an equally decorative way. It also serves as a valuable insect pasture and is generally pleasantly low-maintenance.


The California lilac, botanically Ceanothus, is also commonly called soap bush or buckbrush.

Although it is not related to the lilac, this name is at least a correct indication of its natural area of origin: the California lilac comes mainly from the American west coast, with most of its 60 species from sunny California.

However, some species also occur in eastern and southern parts of the U.S. or even across the border to Mexico and into northern South America.

In its native habitats, the California lilac inhabits dry, rocky, calcareous habitats, mainly rocky forests and coastal areas.

There it does not have to deal with particularly strong frosts, which is why the plant is only conditionally hardy in many regions. However, one of the best-known cultivars, ‘Gloire de Versailles’ of the hybrid species Ceanothus x delilianus, can usually withstand mild winters.

Origin in brief:

  • Area of origin of most species is California.
  • Some species are also distributed in the eastern USA and in Central and South America.
  • Its original habitat are rocky, chalky, barren forests and coastal areas.
  • It is only conditionally hardy.


The many species of the California lilac show partly quite different growth characteristics. With some of them, confusion with the lilac is far away.

However, the popular hybrid Ceanothus x delilianus has some similarities to the lilac in its habit as well as in its flowers.

It grows as an upright shrub with loosely branched, slightly overhanging branches and reaches about 5 ft (1.50 m) in height and width. In very warm and sunny circumstances, it can also reach up to 6.5 ft (2 m) in height.

Some Ceanothus species also grow as low cushions of only a few inches in height and all the more intense spreading growth. In their native areas, they are also used as ground covers.

Growth characteristics at a glance:

  • The California lilac usually grows as an upright shrub with loose branching.
  • Cultivated species usually grow around 5 ft (1.50 m) high and wide.
  • Some species also cover the ground in low cushions.


The leaves of most Ceanothus species have opposite or alternate, oval-shaped leaves about 0.5-2 inches (1-5 cm) long. Their margins are sometimes entire, sometimes slightly serrated or notched.

In some species, a strongly depressed veining forms a crinkly surface texture.

This is not the case with the Ceanothus x delilianus, here the leaves are rather finely textured, pointed at the front, and with a length of more than 3 inches (8 cm) also somewhat larger.

They attach alternately to the twigs, have a rich, medium green color, and are felt-like hairy on the underside.

They do not show fall color and can remain on the shrub in mild winters, but are shed in more severe cold.

Leaf characteristics in short:

  • In most species, rather small, oval, sometimes crinkly leaves.
  • In the hybrid species, somewhat larger, pointed and finely veined.
  • Rich green color, no fall coloration.
  • Depending on weather conditions deciduous or wintergreen.


With its panicle-like bushy inflorescences, which also still appear in bluish to violet, sometimes white or pink colors, the California lilac is indeed clearly reminiscent of the lilac.

The panicles, about 2.5-4 inches (6-10 cm) long, stand at the ends of the young, annual, and lateral shoots and branch loosely. The individual flowers are about only 0.2 inches (0.5 cm) in size and have five teeth.

The flowers also develop a pleasant fragrance, although not as characteristically sweet and intense as the lilac. Bees, bumblebees, and butterflies like to fly over them in large numbers.

Flower characteristics at a glance:

  • Spike flowers, 2.5-4 inches (6-10 cm) long, in blue to purple, pink, or white.
  • Terminal or lateral, loosely branched.
  • Slightly fragrant, valuable insect grazer.

When is Flowering Time for the California Lilac?

The flowers of the California lilac open from July and can sprout again and again until late autumn.

What Kind of Location is Suitable for the California Lilac?

According to its native California, the California lilac needs a location that is as warm and sunny as possible, and preferably protected from sharp winds.

So it should not be too exposed, but best protected on a south-facing house wall.

What Soil Does the California Lilac Need?

When it comes to planting soil, you should also be guided by the origin of the California lilac.

It prefers a rather lean, sandy, calcareous soil with some clay content. If the garden soil is heavy, be sure to incorporate good drainage in the form of a layer of gravel and mix the soil thoroughly with sand.

This is especially important in winter, as otherwise there is a risk of too much wet, freezing cold at the root ball. Relatively high salt and mineral content are also good for the California lilac, which likes to grow near the coast.

Soil requirements in brief:

  • Rather lean, sandy, and calcareous soil.
  • Work good drainage into heavy soils.
  • High salt and mineral content are beneficial.

What is the Best Time to Plant the California Lilac?

A California lilac is best planted in the spring. Because of its sensitivity to frost, which is even more pronounced in the young plant stage, it is quite advisable to wait until mid-to-end May.

California Lilac As a Hedge

A pure hedge of California lilacs can offer you a splendid sight in summer and autumn. At the same time, it is also an effective privacy screen.

When planting a hedge, place the single specimens relatively close together, about a scant 2 feet apart.

Work good drainage into the soil and water the young plants well. Especially in the first winter, they must be well protected from severe frost.

Watering the California Lilac

California lilacs do not have high moisture requirements. After all, their habitat of origin is also a dry one.

So, as a rule, you do not need to water the bush separately. However, newly planted specimens should be watered well and re-watered from time to time during the first few weeks.

In particularly long, hot dry periods in the summer, watering naturally does no harm. However, you should avoid waterlogging at all costs.

Fertilizing the California Lilac Properly

The nutrient requirements of the California lilac are also not high. Therefore, you should refrain from fertilizing, even applying organic slow-release fertilizer such as compost or horn shavings is not necessary.

Pruning the California Lilac Properly

To enjoy a beautifully flowering and well-kept shrub, you should cut back the California lilac annually in spring. Wait for the last heavy frosts to do this.

To encourage vigorous and shapely budding, cut back all of last year’s shoots by about half so that a few buds remain. For young specimens, feel free to prune back a bit more vigorously.

During the flowering period from July to November, regularly cut off any panicles that have stopped flowering to stimulate their regeneration.

Older specimens can also be given a more radical rejuvenation pruning at intervals of about 3 years. This will prevent the shrub from becoming bare and looking unkempt from the inside.

When rejuvenating, cut old, woody branches down to about 15 inches (40 cm), always above an outward-facing eye.

Pruning rules at a glance:

  • Regular pruning in spring promotes abundant blooms and a fuller shrub shape.
  • Cut back old shoots to a few buds.
  • Always cut off flowers that have blossomed during the flowering period.
  • Cut back older specimens more thoroughly every 3 years to rejuvenate them.

Is the California Lilac Winter Hardy?

The winter hardiness of the California lilac is one thing. Actually, it does not really know any significant frosts from its home country.

However, the commonly cultivated hybrid Ceanothus x delilianus, a hybrid of an American and a Mexican California lilac, is considered hardy.

As a precaution, you should cover the root base of the plant a little with fir branches in very severe winter temperatures.

In addition, the following applies to planting: choose a location protected from the wind and ensure sufficient drainage in the planting base, so that the root ball does not freeze through.

What to Do if My California Lilac is Frozen?

If you have neglected the measures for winter protection, the California lilac may well freeze to death.

However, if the bush does not show signs of life in the spring, and you suspect winter damage, do not abandon it immediately. Often, after all, in the plant still hid spirits of life, but they need a while to awaken.

To check and revive the life force of the California lilac, thoroughly cut down the dead shoots in the spring. Once it gets much warmer and sunnier, you can give the plant a boost with a little growth fertilizer.

Unfortunately, if there’s still no action in May and June, the shrub is probably beyond saving.

To remember:

  • Do not abandon frostbitten California lilacs.
  • Thoroughly cut down dead shoots in the spring.
  • Give some (!) growth fertilizer.
  • Observe whether the shrub still sprouts until June.

Yellow Leaves

When the leaves of the California lilac turn yellow, it is usually an indication of too much moisture or too much nutrient supply.

Since it is very sensitive to waterlogging, insufficient drainage in the substrate can quickly be acknowledged accordingly.

When planting, make sure the soil is well-drained and water only during prolonged dry spells, if at all. Place a seedling flower in a container away from the rain.

If you want to jump-start a dead California lilac with fertilizer, you can – but do so extremely sparingly! The not-so-hungry plant can not tolerate too many nutrients.

California Lilac in a Pot

You can also keep a California lilac in a pot if you do not have a garden, but only a balcony or terrace. When growing in a pot, you must pay attention to moderate but regular watering without waterlogging.

In winter, be sure to protect the pot from the cold, preferably by wrapping it in burlap and covering the substrate with fir branches.

Propagating the California Lilac

It is best to propagate the California lilac by cuttings or layering. Seed propagation is also possible in principle, but it is much more time-consuming and does not promise true-to-type new plants.


For the cutting method, it is best to cut a young side shoot in early summer that has not yet produced flowers.

You can briefly dip the cut base, which has been somewhat freed from the bark and leaf bases, in rooting powder before placing it in planting containers with growing medium or cactus soil.

It is best to keep the cuttings evenly moist under foil. The ambient temperature should be warm at a good 68 °F (20 °C), the light should be bright but not directly sunny.

After about 4 weeks they should have rooted and can be transplanted into larger pots.

Cuttings propagation at a glance:

  • In early summer, cut young side shoots that have not yet flowered.
  • Remove bark and leaves from the bottom.
  • Dip in rooting powder and put into growing soil.
  • Root under foil at 68 °F (20 °C) and without direct sunlight.
  • Transplant after approx. 4 weeks.


With the California lilac, it is also quite easy to use layering for propagation. To do this, find a shoot from the previous year that is close to the ground and place it in the surrounding soil.

Make a cut at the place where it should take root and fix it with a metal hook. In the following spring, it should have rooted and can be separated from the mother plant.

Is the California Lilac Poisonous?

Fortunately, the California lilac is not poisonous. So it poses no danger to small children or pets in the garden.


The most common varieties of California lilacs are usually varieties of the hybrid form of American and Mexican California lilacs. But hybrids of other species are also occasionally available.

Ceanothus ‘Gloire de Versailles’

This variety is characterized by its loose, slightly overhanging habit and, of course, its beautiful panicle flowers, which appear in light purple-blue from July.

They delight with a delicate fragrance and with their persistence. They can sprout again and again into November.

The bushy growing shrub reaches a height of about 3-5 ft (1-1.5 m).

Ceanothus impressus ‘Victoria’

This cultivar of the California lilac belongs to the species Ceanothus impresses, commonly known as Santa Barbara ceanothus.

It blooms profusely and slightly earlier than Gloire de Versailles, about late May to June, in a deep blue.

Its dark green foliage is also evergreen, making the variety a good plant for low hedges. It does not grow as tall as the Gloire de Versailles, with a maximum of about 3 ft (1 m).

However, its habit is just as bushy branched. The Ceanothus impressus Victoria is characterized by good winter hardiness and therefore does not threaten to freeze quickly.

It is a good choice for those who live in not so mild regions.

Ceanothus x pallidus ‘Marie Simon’

With the Marie Simon of the hybrid Ceanothus x pallidus, romantics get their money’s worth. This variety decorates the garden from July until October with large, filigree-structured flower panicles in delicate old pink.

It grows loosely and bushily and, like Gloire de Versailles, reaches a height of about 3 to 5 ft (1 to 1.5 m). Like them, however, the Marie Simon is also less hardy and deciduous.

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Daniel Popovic, Owner: (Registered business address: Germany), would like to process personal data with external services. This is not necessary for using the website, but allows me to interact even more closely with them. If desired, please make a choice: