Ceanothus

Ceanothus is a genus of flowering shrubs and small trees in the family Rhamnaceae, comprising about 50 to 60 species. Native to North America, especially western regions, several species are widely cultivated for gardens and landscapes. Commonly known as California lilac, Ceanothus species are not true lilacs (Syringa) but share a showy display of blue to purple flowers in spring. Some species also produce white or pink cultivars.

Most Ceanothus species are evergreen, though some are deciduous in colder climates. They typically have opposite, simple leaves that are often glossy and may bear finely serrated margins. Flower clusters are dense panicles of small, five-petaled flowers, rich in nectar and attractive to bees and butterflies. The fruit is a small, dry, three- or four-lobed capsule that splits to release seeds. Many western species are adapted to Mediterranean climates with dry summers and are drought-tolerant once established.

Ecology and cultivation notes: Ceanothus species frequently form nitrogen-fixing associations with the actinobacteria Frankia in root nodules, which can enrich poor soils. Their seeds often require scarification or exposure to smoke or heat for germination, a trait tied to fire-adapted ecosystems such as chaparral. They provide habitat and forage for wildlife and are used in restoration projects, erosion control, and ornamental plantings.

Distribution and habitat vary by species. In addition to widespread California and Pacific Northwest representatives, Ceanothus americanus is native to eastern North America, where it is known as New Jersey tea. Garden selections exist in a range of sizes from groundcovers to small trees.