Step-by-Step Guide to Growing and Caring for Ceanothus (California Lilacs)

California Lilacs (Ceanothus) are a great choice for adding a splash of vibrant blue to your garden. Ceanothus is a genus that contains around 50 species of drought-tolerant, pollinator friendly, flowering shrubs. The majority of the species are evergreens but some are deciduous. You can use them as informal hedges or border plants. Some gardeners train specific cultivars to climb fences, walls or doorways. California lilacs can be planted in the spring.
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Common Name California lilac, Mountain lilac, Wild lilac
Ceanothus spp.
Family Rhamnaceae
Plant type Evergreen shrubs and deciduous shrubs
Mature Size 2-20 ft. tall
Sun Exposure: Full Sun, Partial Shade
Soil Type Well Drained
Soil pH Acid, Neutral, Alkaline
Bloom time depends on cultivar
Flower Color Pink, Blue, White
Hardiness zones vary depending on cultivar
Native Area North America
California Lilac Care
Ceanothus is easy to grow if you choose the right place. They require shelter from harsh winds and frosts. It is best to grow against a wall that faces south. The majority of cultivars require full sun and a soil that drains well. They also need little or no water after they are established.

Plant the shrub in a place where it will have plenty of space to grow.
California lilac shrub with bright blue flowers spikes and buds

California lilac shrub, with bright and thick spikes of blue flowers
California lilac bush with long stems, blue flowers and clusters.
Honeybee pollinating California lilac flowers closeup
In hotter regions, afternoon shade is beneficial. A lot of shade will lead to disappointing blooms.

California lilacs can grow in most soil types as long as they are well-drained. They prefer fertile soils that are not too heavy or wet. Yellowing leaves can be caused by chalky soils.

You can also plant the shrubs on slopes or mounds to encourage rapid runoff if drainage is not good. You can also amend the soil with organic matter for better drainage.

California lilacs require regular deep watering when they are newly planted. Once established, however, the shrubs can tolerate drought and thrive in arid environments. During prolonged dry, hot spells, additional irrigation may be needed to encourage healthy growth and blossoms. They won’t appreciate additional watering if they don’t. You should do one deep soak rather than little and frequently.

You should let the soil dry out between waterings. Automatic irrigation systems may be problematic for these plants.

Temperature and Humidity
California is home to many ceanothus species that thrive in a Mediterranean climate with warm, wet summers and mild, moist winters.

Evergreens are more susceptible to wind and frost damage than deciduous trees.

They are able to fix nitrogen naturally and thrive in unfertile soils, so there is no need to feed them. If you want to encourage new growth, mulch the base of your shrub with garden compost. Be careful not to mulch the stem.

California Lilacs: Types
Ceanothus are available in many sizes and with different growth habits. There are many more evergreen varieties available. However, if your garden is more exposed to the elements, it makes sense to choose a deciduous species. Popular species cultivars are:

Ceanothus Concha: One of most popular, hardy and adaptable evergreen ceanothus varieties. It grows up to 10 feet tall, with flowers appearing in late spring. It’s better to use it as a specimen than as a wall-trained plant because the branches cascade.
Ceanothus Thyrsiflorus Var. Repens AGM: This is a very hardy evergreen which grows as a large mound. It is often seen cascading down low walls.
Ceanothus Thyrsiflorus: This ceanothus can handle colder temperatures and slower draining soils better than other ceanothus. It also has a longer bloom period.
Ceanothus delileanus AGM: A deciduous shrub that grows through the summer and autumn. It has large glossy green leaves and soft blue flowers. Growing up to 5 feet in height.
These shrubs do not require a lot to be pruned. Hard pruning can cause problems, as it weakens the integrity of evergreens. After the branch has finished blooming, you can keep the shape by only pruning the tips. By lightly pruning the interior branches that are not covered in foliage, you can encourage new growth and improve air circulation. This should be done after the blooming season has ended.

The deciduous cenothus can be pruned more aggressively by cutting off the woody growth of the previous year in early spring.

California Lilacs are propagated by dividing them.
Ceanothus is relatively easy to propagate by cuttings, and will usually flower within two to three seasons. After flowering in the summer or fall, it’s best for evergreens to take cuttings of current-season growth that are semi-ripe. Softwood cuttings can be taken from non-flowering stem tips of deciduous trees in spring.

Dip the cutting into rooting hormone, and place it in a humid warm area (for evergreens, a propagator may be helpful). Before planting, evergreen ceanothus usually needs a full growing season. Deciduous varieties should take four to six weeks for them to root.
California Lilacs: How to grow them from seed
It is possible to grow ceanothus from seeds, but this can be difficult, and the named cultivars will not come true to form when grown in this way.

Due to their dormancy and hard seed coat, they must soak in hot water at least for 24 hours. Then you’ll need to stratify the seeds for about three months. You need to keep them warm (60 to 65 degrees Fahrenheit) when you sow the seeds. Germination can take three months.

Common Plant Diseases & Pests
The fact that ceanothus are not plagued by many pests and diseases is one of their most attractive features. They can, however, be affected by scale insects and honey fungus.

California Lilacs in Bloom
California lilacs’ abundant blooms attract gardeners and pollinators like bees. The small flowers are arranged in clusters and can last up to six weeks.

The length and timing of blooming depends on the cultivar and species. Some bloom from late spring through summer while others flower from summer into fall. The majority of cultivars have blue flowers, but some produce white or even pink ones. Ceanothus (Perle Rose AGM) is a deciduous cultivar with bright pink flowers. Ceanothus x pallidus (Perle Rose) AGM is a deciduous cultivar that has bright pink blooms.

It’s not practical to deadhead cenothus, given how many flowers they produce. However, you can remove the spent blooms in order to improve vigor and maintain a neat look. Overwatering and too much shade can affect bloom success.

Ceanothus: Common problems
Ceanothus can be a simple plant to grow. However, if you don’t provide the right conditions, it will have problems. These include:

Root rot can be caused by soils that are too wet or poorly draining
Lack of nutrients can cause yellowing of the foliage in soils with chalky texture
If your shrub is placed in a location that is too exposed, it is possible to suffer frost and wind damage.
How long do California lilacs last?
Ceanothus is a fast-growing plant, but it does not live long. Deciduous species may live up to 15 years but evergreens might not. When they begin to lose shape and become leggy and straggly, you’ll know that they are nearing the end of life.

Can you grow ceanothus indoors?
These species don’t grow well in the home. These plants are spreaders and thrive when they can extend their roots.

How can I teach evergreen ceanothus how to climb a wall?
Use horizontal wires, a trellis or vertical wires to tie the main stem of the shrub. You can tie in the side branches by spreading them out. After flowering, remove branches that extend beyond the wall and train new shoots into gaps.