Ceanothus americanus.jpg
Ceanothus americanus flowers
Scientific classification

See text

Ceanothus L. s/[2] is a genus of about 50–60 species of nitrogen-fixing[3] shrubs or small trees in the family Rhamnaceae.[4] Common names for members of this genus are California lilac, wild lilac, and soap bush.[5] "Ceonothus" comes from a Greek word meaning "spiny plant",[5] Ancient Greek: κεάνωθος (keanōthos), which was applied by Theophrastus (371–287 BC) to an Old World plant believed to be Cirsium arvense.[6][7]

The genus is endemic 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 metres (1.6–9.8 ft) tall, but C. arboreus and C. thyrsiflorus, both native to California, can be small multi-trunked trees up to 6–7 metres (20–23 ft) tall.


Ceanothus arboreus, illustrating the three parallel leaf veins characteristic of this genus.

Growth pattern

The majority[citation needed] 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.

Leaves and stems

Ceanothus leaves may be arranged opposite to each other on the stem, or alternate. Alternate leaves may have either one or three main veins rising from the base of the leaf.[8]

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.[9]

Flowers and fruit

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,[citation needed] and Ceanothus species are typically dependent on forest fires to trigger germination of their seeds.[9]

Fruits are hard, nutlike capsules.[5]

Other Languages
català: Ceanothus
Cebuano: Ceanothus
čeština: Latnatec
dansk: Ceanothus
Deutsch: Säckelblumen
Diné bizaad: Chʼįdą́ą́ʼ
español: Ceanothus
français: Céanothe
português: Ceanothus
svenska: Ceanothus
Winaray: Ceanothus