California Lilac ~ Ceanothus thyrsiflorus Plant Care Guide

Ceanothus thyrsiflorus, known as blueblossom or blue blossom ceanothus, is an evergreen shrub in the genus Ceanothus that is endemic to California. The term ‘Californian lilac’ is also applied to this and other varieties of ceanothus, though it is not closely related to Syringa, the true lilac.

C. thyrsiflorus can grow more than 6 m (20 ft) tall in its native chaparral habitat. Flowers vary from different shades of blue to close to white. It is popular with birds, butterflies, and other pollinators.

Cultivars

C. thyrsiflorus has been used in gardens extensively, and several cultivars have been selected. Popular garden varieties include:-

• ‘Blue Mound’ which can grow to 1.5 m (4 ft 11 in) tall
• ‘Cascade’ which may reach 8 m (26 ft) of height
• ‘El Dorado’, a variegated cultivar with gold edge foliage and powder blue flowers^[1]
• ‘Repens’ which stays as a shrub around 1–3 m (3 ft 3 in–9 ft 10 in) tall
• ‘Repens Victoria’, forming a sturdy evergreen mound and most useful groundcover with powder blue flowers
• ‘Skylark’, a tall type with blue flowers (this cultivar has gained the Royal Horticultural Society‘s Award of Garden Merit)^[2]
• ‘Snow Flurry’, with white flowers

See also

• California chaparral and woodlands
• California montane chaparral and woodlands
• California native plants

How to Care for California Lilac Shrubs

You guessed it — the California lilac (Ceanothus spp.) is native to California. Known also as blue blossom or mountain lilac, it is perfect for the gardener who tends to neglect the garden a bit. However, to ensure that your California lilac thrives, give it some care and attention, especially in the first growing season and during hot weather. Then enjoy its annual spring and summer display of colorful flowers for years to come. Most California lilacs grow well in U.S. Department of Agriculture Plant Hardiness Zones 8 through 10.

1. Water a California lilac one or two times a week with 1 inch of water for its first growing season. For more drought-tolerant varieties, such as Ceanothus thyrsiflorus, gradually reduce how frequently you water it during the second year; in subsequent years, water these varieties once every three or four weeks. Water other California lilacs, such as Ceanothus maritimus, about once a week, especially during hot weather.

2. Clip off blooms after they fade to keep the shrub tidy. Cut back new growth to healthy leaf sets while it is actively growing to control the shrub’s size. Do not cut branches that are more than 1 inch in diameter.

3. Fertilize California lilac every spring just as the leaf buds begin to swell. Use an all-purpose fertilizer, such as 10-10-10. Apply no more than the amount specified by the manufacturer, sprinkling it evenly under the shrub’s canopy, then water in the fertilizer with 1 inch of water.

4. Examine your shrub occasionally, looking for signs of insects and their damage, such as aphids on the underside of the leaves or browning leaf tips. Prune affected branches in small infestations to a set of healthy leaves and discard. Treat heavier infestations with an appropriate organic/natural remedy.

Things You Will Need

• Garden hose
• Pruning shears
• Fertilizer

Tip

• California lilacs do not like wet feet or standing water, so plant in soil that drains well.
• If your soil is rich in organic matter and your California lilac grows well without it, do not fertilize.

References

• Learn2Grow: Ceanothus Thyrsiflorus
• Oregon State University Extension Service: Blueblossom
• Monrovia: Ceanothus
• Washington State University: Ceanothus, Commonly Known as California Lilac
• Washington State University: Blue Blossom

Resources

• Sunset: Ceanothus Thyrsiflorus
• Monrovia: Victoria California Lilac

About the Author

Melissa Lewis is a former elementary classroom teacher and media specialist. She has also written for various online publications. Lewis holds a Bachelor of Arts in psychology from the University of Maryland Baltimore County.

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See Also ….

Ceanothus thyrsiflorus Eschsch. Blue blossom, Blueblossom, Bluebrush Rhamnaceae (Buckthorn Family)

Ceanothus thyrsiflorus var. repens AGM

California Lilacs (Ceanothus spp.)

Ceanothus thyrsiflorus Growing Profile