Ceanothus L. ( /ˌsiːəˈnoʊθəs/) 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.