Our native Ceanothus on the property is currently exhibiting a profusion of bloom. A large specimen tree near the house is all a-buzz with bees. If you stand beneath these trees, there’s a low background audible hum that emanates from above, along with a gentle shower of blossoms and pollen as numerous insects travel between the flower clusters.
Ceanothus thyrsiflorus, also known as Blue Blossom Ceanothus, belongs to the Rhamnaceae (Buckthorn) family, and is a Pacific Coast native, ranging from Santa Barbara County, California, to southern Oregon. In its native habitat, this species favors coastal redwood forest, chaparral, and mixed evergreen forests, or northern coastal scrub.
The name thyrsiflorus, means thyrse-flower, referring to the dense, branched flower cluster; traditionally thyrsus is the name given to the Giant Fennel staff, adorned with ivy, leaves, and berries, topped with a pine-cone, and carried by Bacchic maenads in Greek Mythology.
Ceanothus thrysiflorus is the largest of our native Ceanothus species, often reaching more than 20 feet tall. We’ve observed at least four specimens on the property that exceed 20 feet in height, and numerous younger shrubby vase-shaped specimens.
We’ve noticed on the tree shown above that the deer have done some significant damage, not just from browsing the branches, but also rubbing against the bark.
Although both deer and rabbits are both known to browse the foliage of Ceanothus thyrsiflorus, this tree is fortunately now within the deer fence boundary, behind the vegetable gardens, and hopefully won’t sustain much additional damage.
Otherwise few pests, except occasional aphids, seem to be a problem.
The leaves of Ceanothus thyrsiflorus are evergreen, oblong-ovate, shiny on the upper surface, and typical of Ceanothus they are 3-ribbed from base.
The fragrant flowers emerge between March and June, and are generally a pale blue, with each flower panicle averaging 2-3 inches long.
The flowers persist for a few weeks, attracting all sorts of insects, and spiders.
The tiny fruits form in tight grape-like clusters, and the seeds are released in mid-late summer, almost explosively, and are favored by wildlife. Here the chipmunks on the property have been observed gorging themselves in late summer on the bounty of seeds shed across the deck near the house.
In the few years we’ve been here we’ve noted that the degree of bloom seems variable. Last year the plants produced scant blooms, and few seeds, perhaps as a result of drought, as none of our wild specimens receive any supplemental irrigation. This year however, after a significantly wet spring, masses of flowers are being produced.
Native American tribes, including the Pomo and Kashaya, have traditionally used Ceanothus thyrsiflorus blossoms for ceremonial dance wreaths. They also mixed fresh or dried flowers with water to use as a soap for washing the hands, face and body, and the Polikah tribe would use a decoction of twigs and leaves for washing newborn babies.
Ceanothus thyrsiflorus, unlike some Ceanothus species, is reportedly relatively long-lived, and will tolerate a variety soil types. In hot summer regions these plants do benefit significantly from supplemental irrigation. As we have lost some C. thyrsiflorus in the last couple of years, possibly secondary to drought stress, for those specimens now enclosed within the orchard fence, we will route some drip irrigation to help them during particularly hot dry periods in late summer.
To replace the plants we’ve lost, we’d like to try propagating this plant this fall. The most economical method for propagating Ceanothus thyrsiflorus is from seed. We will wait until the seed clusters ripen on the trees this summer, and try to harvest some seed before the seed capsules explode. As the seeds have a hard outer coat, it is recommended that the seeds first be soaked in a cup of hot water, and left overnight. The seeds can then be sown in flats, and as they grow they can then be transferred to successively larger pots. It is important not to allow the plants to become pot-bound. Alternatively, the seed is held until fall, and sown directly in native soil, where the cool winter nights reportedly help to stimulate germination.
Just because Ceanothus is native to the Pacific west, doesn’t mean you won’t see it elsewhere. “The Royal Horticultural Society of England received seeds of Ceanothus thyrisflorus from Richard Brinsley Hinds, surgeon-naturalist on the expedition of H.M.S. Sulphur, in 1837, making it the first California species introduced into European gardens. It remains common in British Gardens today”
Note that Ceanothus thyrsiflorus is one of hundreds of known host plants for Sudden Oak Death, and its movement may be subject to restrictions in some California counties.
 Daniel E. Moerman’s Native American Ethnobotanical Database
 Fross, David, and Wilken, Dieter. Ceanothus. 2006. Timber Press, Incorporated.