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San Diego Ceanothus Back to Plant Page
Ceanothus cyaneus

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About San Diego Ceanothus (Ceanothus cyaneus) Ceanothus cyaneus is a rare species of flowering shrub known by the common names San Diego Ceanothus and Lakeside Ceanothus. This Ceanothus is found in the mountains of San Diego County, California, and its range probably extends just into Baja California. Most of the remaining natural specimens are in a small area in the hills around Lakeside and Ramona in San Diego County. This is a tall, erect shrub which may approach 5 meters in height. Its spreading branches are gray-green, with the younger twigs a light greenish-brown. The evergreen leaves may be serrated and toothed with hairy knobs, or they may be smooth along the edges. The underside is a lighter green than the upper surface. The flower cluster may exceed 15 centimeters in length, bearing many bunches of flowers along the length of a greenish stalk. The long flowers are bright blue with protruding yellow anthers. The capsule fruits are about 4 millimeters long.

Ceanothus cyaneus can be tricky to grow in landscaping applications. After the first year, direct summer water will usually kill it, but it will often also die if it can't get it's roots to moisture over the summer. It's best to plant on dry rocky slopes near a damper area, such as a seasonal creek, or near an irrigated area, or even 5-10 feet from a bubbler. It does best if surrounded by rocks or other plants that can shade its roots from the sun. If happy, it produces profuse displays of flower ranging from bright blue to powder blue to lavender in color. It does best on north facing slopes, but can also handle east or west facing slopes if there is nearby water.
Plant Description
Plant Type

Max. Height
8 - 16.4 ft (2.4 - 5 m)

Max. Width
12 ft (3.7 m)


Fragrant - Pleasant

Growth Rate


Flower Color

Flowering Season
Spring, Winter

Native Status
Natural Setting
Site Type
Dry rocky slopes, foothills and inland valleys among chaparral primarily in the Peninsular Range of San Diego County. At higher elevations, also found in conjunction with pine forest

Sun, Part Shade

Elevation ?
339' - 4641'

Annual Precip. ?
10.8" - 35.2"

Summer Precip. ?
0.31" - 1.82"

Coldest Month ?
43.4° F - 54.6° F

Hottest Month ?
67.1° F - 78.5° F

Humidity ?
1.04 vpd - 26.88 vpd

Soil Description
Tolerates clay soil but does best in well drained decomposed granite

Soil PH
6.0 - 8.0


Cold Tolerance(° F)
Tolerates cold to 25° F

Companion Plants
Use with other chaparral plants of southern California such as Manzanitas (Arctostahpylos species), Toyon (Heteromeles arbutifolia), Lemonadeberry (Rhus integrifolia), California Encelia (Encelia californica), Sagebrush (Artemisia californica), California Buckwheat (Eriogonum fasciculatum), Chamise (Adenostem fasciculatum), Bush Rue (Cneoridium dumosum), Tree Poppy (Dendromecon rigida), Thickleaf Yerba Santa (Eriodictyon crassifolium), Flannel Bush (Fremontodendron species), Mallow (Malacothamnus species), Scrub Oak (Quercus berberidifolia), Sages (Salvia species), Dudleya species, cactus species and annuals.

Wildlife Attracted
Very popular with bees and butterflies. Plants in the Ceanothus genus are host plants to the Spring Azure, Echo Blue, Pacuvius Duskywing, California Tortoiseshell, Pale Swallowtail, and Hedgerow Hairstreak butterflies.

Landscaping Information
Ease of Care
Moderately Easy

Water Requirement ?
Extremely Low
Very Low
Moderate - High

Seldom Used

Max. Summer Water ?
No Summer Water
No Summer Water
Keep moist

Organic with Rocks

Pruning is recommended to control its tendency toward straggly growth. Prune to desired shape in dry season to prevent infection.

Propagation ?
For propagating by seed: Hot water; then 3 mos. stratification may improve germination.

Common uses
Bank Stabilization, Bird Gardens, Butterfly Gardens, Bee Gardens

Nursery Availability
Commonly Available

Other Names
Common Names
San Diego Buckbrush, Lakeside Ceanothus

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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