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Ceanothus- The California Lilac

It may seem foolhardy to address the huge Ceanothus complex in a short article. However, here is a very rudimentary treatment, with emphasis on the horticultural varieties. The Ceanothus genus is in the Rhamnaceae family and is divided into two subgenera, the Ceanothus and the Cerastes. This is important distinction. Plants in the Ceanothus subgenus have round to linear leaves with smooth margins and an alternate branching pattern. They require more water and deer seem to like the fleshier leaves. Ceanothus foliosus, wavy-leaved, and C. thyrsiflorus are members of this subgenus. Plants in the Cerastes subgenus have conspicuously toothed, holly-like leaves with a thick, leathery texture. The branches and leaves are oppositely arranged. Ceanothus sonomensis, C. maritimus and C. confusus (Rincon Ridge Ceanothus) are members of the Cerastes subgenus. Plants in this section are the most drought tolerant and deer resistant.

Early pioneers, with an understandable longing for familiar plants, graced it with the common name, California lilac, referring to the spring blooming panicle of small, blue flowers. (Aside: there are exceptions to all Ceanothus generalizations, the first is that some species have white flowers.) You can plant these evergreen shrubs as a shrubby groundcover, as a foundation planting, as a hedge, as a small tree, or as part of a shrub border.

As we would expect from plants that are native to the chaparral regions of the state, Ceanothus are drought tolerant, hence their value in California gardens. Ceanothus have a reputation for being short lived. This is often a problem of poor placement and poor management. Although, in my experience, they do not live as long as manzanitas and other native shrubs. They require good drainage and are short-lived in wet clay soils where too much water on their roots invite fungus diseases such as root rot. Ceanothus grow rapidly to their ultimate size. Prune in the warm months for rapid healing. Regulate the size by pinching out new shoots, rather than waiting until they are out of control and require radical surgery.

The modern cultivars that are sold in nurseries have proved to do well in our gardens and some will adjust to regular garden watering. Here is a brief introduction to some of those that are available:

• Groundcover types are Ceanothus gloriosus var. ‘Emily Brown’, ‘Heart’s Desire’, and ‘Anchor Bay’ (Cerastes). Other selections from the Cerastes subgenus are Ceanothus maritimus ‘Point Sierra’ and ‘Valley Violet’. C. hearstiorum and C. griseus horizontalis ‘Carmel Creeper’ and ‘Yankee Point’(Ceanothus). These will grow to cover an area of about 5 feet.
• Mid-size shrubs that grow between 6’ to 8’ are C. impressus ‘Julia Phelps’ and ‘Dark Star’ which both bloom with brilliant cobalt blue flowers. Watch for them now, they are hard to miss! Other mid-size cultivars are C. ‘Concha’ and ‘Joyce Coulter’, and C. thyrsiflorus ‘Skylark’. All of these are in the Ceanothus subgenus.
• A very large shrub is C. arboreus, a native to the Channel Islands; in the trade one usually finds C. arboreus x griseus ‘Ray Hartman’. C arboreus ‘Cliff Schmidt’ is available at Cal Flora Nursery. Both can be trained to be a small (15’) evergreen tree or grown as a large shrub. C. thyrsiflorus commonly called blue blossom, is native to the Coast Ranges and can grow to 20 feet. Inland it appreciates some shade which will moderate the growth. Two C. thyrsiflorus varieties available are ‘Oregon Mist’ and ‘Snow Flurry’ which has masses of white flowers.

There are many other cultivars available. Check the Cal Flora Nursery website or visit their nursery in Fulton. The new Jepson (2012) lists 46 species and numerous sub-species that are found growing in California, so one can spend quite a bit of time getting to know this fascinating shrub group. There is a Timber Press book devoted to them by Fross and Wilkins published in 2006. The Sunset Garden Book has good information on the most common cultivars. If you enjoy old Fremontias, as I do, you will find information on the species origin of many cultivars in the January 1994 issue. The January 1987 issue has an article by Nevin Smith on cultivating Ceanothus.

I hope that I have piqued your interest with this brief account. Remember as you visit gardens and nurseries this spring to keep an eye out for blooming Ceanothus, and perhaps you might buy one or two. The best way to find out about any plant is to grow it in your garden.

Liz Parsons

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