Elizabeth is a Permaculture Garden Designer, Sustainability Consultant and Professional Writer, working as an advocate for positive change. She graduated from the University of St. Andrews with an MA in English and Philosophy and obtained a Diploma in Applied Permaculture Design from the Permaculture Association.
Reviewed By ROY NICOL
Roy is a Professional Gardener and Horticultural Consultant, specialising in large garden year-round maintenance and garden development. He is an RHS Master of Horticulture and uses his research in the application of no-dig methods in ornamental garden settings. Roy has been a Professional Gardener for more than six years and is a member of the Chartered Institute of Horticulture, Professional Gardener's Guild and Association of Professional Landscapers (Professional Gardener).
Contributions From PETER LICKORISH
Peter is a Horticulture Lecturer and self-employed Horticulturist, with a passion for diverse areas of the industry - from garden design to the science behind plant growth and propagation. He has completed the Royal Horticultural Society’s Master of Horticulture (MHort) Award and lectures on RHS courses at Bedford College.
IN THIS GUIDE
- 1) C. arboreus ‘Trewithen Blue’
- 2) C. ‘Blue Mound’
- 3) C. ‘Cascade’
- 4) C. ‘Concha’
- 5) C. ‘Dark Star’
- 6) C. griseus var. horizontalis ‘Silver Surprise’
- 7) C. ‘Puget Blue’
- 8) C. ‘Southmead’
- 9) C. thyrsiflorus ‘Millerton Point’
- 10) C. thyrsiflorus ‘Mystery Blue’
- 11) C. thyrsiflorus ‘Snow Flurry’
- 12) C. thyrsiflorus var. repens
- 13) C. ‘Skylark’
- 14) C. × veitchianus
- 15) C. ‘Autumnal Blue’
- 16) C. ‘Burkwoodii’
- 17) C. × delileanus ‘Gloire de Versailles’
- 18) Ceanothus × delileanus ‘Henri Desfossé’
- 19) C. × delileanus ‘Topaze’
- 20) C. × pallidus ‘Perle Rose’
- References
Ceanothus, also known as the Californian lilac, is a genus that offers an impressive variety of stunning, flowering shrubs.
These are not only attractive plants, but they also fix nitrogen and attract pollinators in a garden.1The Nitrogen-Fixing Capacity of Ceanothus velutinus. (n.d.). Forest Science. Retrieved March 14, 2023, from https://academic.oup.com/forestscience/article-abstract/12/2/164/4709415
Mostly flowering in a vivid blue but also offering a few options in white or pink, these shrubs can look great in many gardens.
“For something unusual, consider Ceanothus prostratus,” says RHS Master of Horticulture candidate Peter Lickorish.
“The ‘prostrate’ in its name means it is lower growing and forms a carpet of blue flowers for groundcover.”
All of the varieties mentioned in this list are H4 hardy and need to be grown in full sun, in a sheltered position.
1) C. arboreus ‘Trewithen Blue’
- COMMON NAME(S): Californian lilac ‘Trewithen Blue’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
Growing up to around 6m tall, this large spreading evergreen shrub has oval or rounded leaves up to 8cm long.
The flowers, borne in 12cm long panicles, are deep blue and slightly fragrant.
2) C. ‘Blue Mound’
- COMMON NAME(S): Californian lilac ‘Blue Mound’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This cultivar grows to around 1.5m high, and up to 2.5m wide.
Bushy in habit, it has glossy leaves and in the late spring, bears heads of small, bright blue flowers.
3) C. ‘Cascade’
- COMMON NAME(S): Californian lilac ‘Cascade’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
A vigorous evergreen California lilac, this option grows around 4m tall and wide.
The branches are arching, with glossy, ovate leaves.
The clear, light blue flowers are borne in panicles around 8cm in length.
4) C. ‘Concha’
- COMMON NAME(S): Californian lilac ‘Concha’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
Around 3m in height and spread, this ceanothus cultivar has arching branches and narrow, dark green leaves.
The flowers are of a deep blue and bloom in profuse clusters in the spring.
This cultivar has received the RHS Award of Garden Merit (AGM).
5) C. ‘Dark Star’
- COMMON NAME(S): Californian lilac ‘dark star’
- FLOWERS: Blue and purple
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
A spreading evergreen shrub growing around 2.5m tall and wide, this ceanothus has dark green, ovate leaves.
In the late spring, it bears clusters of deep blue-purple flowers on its arching branches.
6) C. griseus var. horizontalis ‘Silver Surprise’
- COMMON NAME(S): Californian lilac ‘Silver Surprise’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: Chalk, loam or sand; alkaline to neutral pH
Growing to 1m or so tall, and spreading 1.5m wide, this low-growing ceanothus has irregular, variegated leaves with creamy margins around the edges.
Masses of pale blue flowers are borne on the shrub in spring.
This variety is H3 hardy.
7) C. ‘Puget Blue’
- COMMON NAME(S): Californian lilac ‘Puget Blue’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: all soil types; any pH
Growing up to around 2.5m tall and wide, this medium-sized ceanothus shrub has small, dark green, narrow leaves.
The flowers are a rich blue-purple and are borne abundantly in panicles in late spring and early summer.
This cultivar has received the RHS Award of Garden Merit (AGM).
8) C. ‘Southmead’
- COMMON NAME(S): Californian lilac ‘Southmead’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: all soil types; any pH
A compact ceanothus growing up to around 1.5m tall and wide, this option is compact, with small oblong leaves with ridges of a dark green hue.
The clusters of dark blue flowers appear in the late spring and in early summer.
9) C. thyrsiflorus ‘Millerton Point’
- COMMON NAME(S): Californian lilac ‘Millerton Point’
- FLOWERS: Creamy white
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: Clay, loam or sand; alkaline to neutral pH
Around 3m in height and spread, this ceanothus has arching branches and small, glossy leaves in a mid-green colour.
The flowers are not blue as with most ceanothus but are a creamy white hue.
So, if you want to ring the changes, this could be an interesting option to consider.
10) C. thyrsiflorus ‘Mystery Blue’
- COMMON NAME(S): Californian lilac ‘Mystery Blue’
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: Chalk, loam or sand; any pH
Spreading to around 3m wide and 2.5m high, this airy and open-structured shrub has dark green leaves on green stems.
The flowers bloom abundantly and are honey-scented.
They are blue to blue-grey in colour.
11) C. thyrsiflorus ‘Snow Flurry’
- COMMON NAME(S): Ceanothus ‘Snow Flurry’
- FLOWERS: White
- FLOWERING SEASON(S): Spring
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This is another ceanothus with a difference.
It bears pure white clusters of flowers in the spring, on a small evergreen shrub up to 1.2m tall, with arching branches and glossy green leaves.
12) C. thyrsiflorus var. repens
- COMMON NAME(S): Creeping blue blossom
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This is a great ground cover plant, as it is relatively low-growing at 1m in height, though it can grow taller when grown against a wall.
The leaves are ovate and dark glossy green.
The flowers are light vivid blue and are borne in spring and early summer in compact panicles.
This cultivar has received the RHS Award of Garden Merit (AGM).
13) C. ‘Skylark’
- COMMON NAME(S): Californian lilac ‘Skylark’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
A compact shrub, growing up to around 2.5m tall and wide, this ceanothus has finely toothed, glossy, dark green foliage.
The clusters of deep blue-purple flowers are borne in the early summer.
This is another recipient of an AGM.
14) C. × veitchianus
- COMMON NAME(S): Veitch’s blue blossom
- FLOWERS: Blue
- FLOWERING SEASON(S): Spring / Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This blue-blossomed variety is a bushy, vigorous evergreen shrub which grows up to around 3m tall and wide.
It has small, wedge-shaped, glossy leaves.
The flowers, which bloom in the late spring and the early summer, are deep blue and are held in 5cm long clusters.
15) C. ‘Autumnal Blue’
- COMMON NAME(S): Californian lilac ‘Autumnal Blue’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer / Autumn
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This is an evergreen option, which bears its oblong trusses of mid-blue flowers from late summer.
It has dark green, glossy, ovate leaves and grows with a bushy habit to around 3m tall.
This cultivar is a recipient of an RHS AGM.
16) C. ‘Burkwoodii’
- COMMON NAME(S): Californian lilac ‘Burkwoodii’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer / Autumn
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This compact evergreen ceanothus grows to around 1.5m tall and wide.
It has shiny, rounded leaves, which are grey and somewhat hairy on the undersides.
The small, rich blue flowers are borne in rounded clusters to 6cm long in the late summer and autumn.
This cultivar has received the RHS Award of Garden Merit.
17) C. × delileanus ‘Gloire de Versailles’
- COMMON NAME(S): Californian lilac ‘Gloire de Versailles’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer / Autumn
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
Growing up to around 1.5m tall with a similar spread, this is one deciduous option to consider.
It has broadly oval, light-green leaves that are around 8cm long.
The flowers are displayed as large clusters in a powder blue colour and are scented.
Another RHS AGM cultivar.
18) Ceanothus × delileanus ‘Henri Desfossé’
- COMMON NAME(S): Californian lilac ‘Henri Desfossé’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
Another deciduous ceanothus, this one also grows around 1.5m tall and wide.
It has oval-shaped, mid-green leaves up to 7cm in length and a rounded growth habit.
The deep blue flowers are borne in panicles 8-12cm across.
19) C. × delileanus ‘Topaze’
- COMMON NAME(S): Californian lilac ‘Topaze’
- FLOWERS: Blue
- FLOWERING SEASON(S): Summer / Autumn
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This deciduous ceanothus also has a rounded, bushy habit and grows to around 1.5 m in height, with a similar spread.
The leaves are light green and broadly ovate, and the indigo-blue flowers are borne in impressive, large panicles in late summer and autumn.
20) C. × pallidus ‘Perle Rose’
- COMMON NAME(S): Californian lilac ‘Perle Rose’
- FLOWERS: Pink
- FLOWERING SEASON(S): Summer
- SOIL PREFERENCE: all soil types; alkaline to neutral pH
This unusual ceanothus has pale, rose-pink flowers rather than the usual blue.
This is another deciduous option, with flowers borne in terminal panicles that reach around 6cm long.
Small and bushy, this ceanothus will grow to around 1.5m tall with a similar spread.
Of course, these ceanothuses are not the only options that you might choose, but all of the above are among the best options to consider.
