Ceanothus L. (pron.: //) is a genus of about 50–60 species of shrubs or small trees in the family Rhamnaceae. The genus is confined to North America, with the center of its distribution in California. Some species (e.g. C. americanus) are found in the eastern United States and southeast Canada, and others (e.g. C. coeruleus) extend as far south as Guatemala. Most are shrubs 0.5–3 m tall, but C. arboreus and C. thyrsiflorus, both from California, can be small trees up to 6–7 m tall. The name is derived from the Greek word κεανοθος (keanothos), which was applied by Theophrastus (371-287 BC) to a spiny Old World plant believed to be Cirsium arvense.
The majority of the species are evergreen, but the handful of species adapted to cold winters are deciduous. The leaves are opposite or alternate (depending on species), small (typically 1–5 cm long), simple, and mostly with serrated margins.
Ceanothus species are easily identified by their unique leaf-vein structure shared by all plants within this genus. The leaves have three very prominent parallel veins extending from the leaf base to the outer margins of the leaf tips and the leaves are ovate in shape. The leaves have a shiny upper surface that feels "gummy" when pinched between the thumb and forefinger, and the roots of most species have red inner root bark.
The flowers are white, greenish–white, blue, dark purple-blue, pale purple or pink, maturing into a dry, three-lobed seed capsule.
The flowers are tiny and produced in large, dense clusters. A few species are reported to be intensely fragrant almost to the point of being nauseating, and are said to resemble the odor of "boiling honey in an enclosed area." The seeds of this plant can lie dormant for hundreds of years, and Ceanothus species are typically dependent on forest fires to trigger germination of its seeds.
Ceanothus is a good source of nutrition for deer, specifically mule deer on the west coast of the USA. However, the leaves are not as nutritious from late spring to early fall as they are in early spring. Porcupines and quail have also been seen eating stems and seeds of these shrubs. The leaves are a good source of protein and the stems and leaves have been found to contain a high amount of calcium.
Plants in this genus are widely distributed and can be found on dry, sunny hillsides from coastal scrub lands to open forest clearings up to 9,000 feet. These plants are profusely distributed throughout the Rocky Mountains from British Columbia south through Colorado, the Cascades of Oregon and California, and the Coastal Ranges of California.
Many species are popular garden ornamental plants, and dozens of hybrids and cultivars have been selected, such as 'Flexible ceanothus', Ceanothus × flexilis Greene ex McMinn (C. cuneatus × C. prostratus).
Propagation of ceanothus is by seed, following scarification and stratification. Seeds are soaked in water for 12 hours followed by chilling at 1 °C for one to three months. It can also sprout from roots and/or stems. Seeds are stored in plant litter in large quantities. It is estimated that there are about two million seeds per acre in forest habitats. Seeds are dispersed propulsively from capsules and, it has been estimated, can remain viable for hundreds of years. In habitat, the seeds of plants in this genus only germinate in response to range fires and forest fires.
Native Americans used the dried leaves of this plant as a herbal tea, and early pioneers used the plant as a substitute for black tea. Miwok Indians of California made baskets from ceanothus branches. C. integerrimus has been used by North American tribes to ease childbirth.
The Californian species are sometimes known as California lilac, but species found elsewhere have other common names, such as New Jersey tea for C. americanus (as its leaves were used as a black tea substitute during colonial times). In garden use, most are simply called by their scientific names or an adaptation of the scientific name, such as 'Maritime ceanothus' for C. maritimus.
Formerly placed here
- Adolphia infesta (Kunth) Meisn. (as C. infesta Kunth)
- Colubrina arborescens (Mill.) Sarg. (as C. arborescens Mill.)
- Colubrina asiatica (L.) Brongn. (as C. asiaticus L.)
- Colubrina elliptica (Sw.) Brizicky & W.L.Stern (as C. reclinata L’Hér.)
- Noltea africana (L.) Endl. (as C. africanus L.)
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- "Genus: Ceanothus L.". Germplasm Resources Information Network. United States Department of Agriculture. 2004-02-10. http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?2210. Retrieved 2012-04-25.
- Sunset Western Garden Book, 1995:606–607
- Elmore, Francis H. (1976). Trees and Shrubs of the Southwest Uplands. Western National Parks Association. pp. 195. ISBN 0-911408-41-X.
- Austin, Daniel F. (2004). Florida Ethnobotany. CRC Press. p. 291. ISBN 978-0-8493-2332-4. http://books.google.com/?id=eS7lX_rC3GEC.
- Edible and Medicinal Plants of the West, Gregory L. Tilford, ISBN 0-87842-359-1
- Coladonato, Milo (1993). "Ceanothus americanus". Fire Effects Information System (online). Rocky Mountain Research Station, Fire Sciences Laboratory (Producer): U.S.D.A; Forest Service. http://www.fs.fed.us/database/feis/plants/shrub/ceaame/all.html. Retrieved August 22, 2010.
- "Ceanothus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=28453. Retrieved 2012-04-25.
- "GRIN Species Records of Ceanothus". Germplasm Resources Information Network. United States Department of Agriculture. http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?2210. Retrieved 2012-04-25.
- University of Wisconsin–Stevens Point Plant Database: Ceanothus americanus
- Moerman, D. (1988). Native American Ethnobotany. Timber Press, Oregon.