Ceanothus L.
Ceanothus is an American genus and counts ca. 58 species ranging from the U.S.A. to Central America (Schmidt & Wilken 2016). The genus is most diverse in the western U.S.A. with 42 species endemic to California. Most species have colourful inflorescences and at least 39 are cultivated as ornamentals in Europe (McKean 1997). Hybridisation frequently occurs, in the wild as well as in cultivation. One (notho-)species, probably the most popular in cultivation, has been recorded as an outcast. Ceanothus xdelileanus, a hybrid of C. americanus L. and C. coeruleus Lag.
Literature:
Fross D. & Wilken D. (2006) Ceanothus. Timber Press, Oregon.
Gardiner J. (1997) Ceanothus. The Garden 122(5): 308-311.
Hardig T.M., Soltis P.S. & Soltis D.E. (2000) Diversification of the North American shrub genus Ceanothus (Rhamnaceae): conflicting phylogenies from nuclear ribosomal DNA and chloroplast DNA. Amer. J. Bot. 87(1): 108-123. [available online at: https://www.researchgate.net/publication/12677314_Diversification_of_the...
Hop M.E.C.M. (2006) Ceanothus – sortimentsonderzoek en keuringsrapport. Dendroflora 43: 80-123.
Jeong S.-C., Liston A. & Myrold D.D. (1997) Molecular phylogeny of the genus Ceanothus (Rhamnaceae) using rbc L and ndh F sequences. Theoretical and Applied Genetics 94(6-7): 852-857.
McKean D.R. (1997) Ceanothus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 185-189.
Nobs M.A. (1963) Experimental studies on species relationships in Ceanothus. Publ. Carnegie Inst. Wash. 623.
Schmidt C.L. & Wilken D.H. (2016) Ceanothus. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 12. Oxford University Press, New York-Oxford. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=105966]
Smith M.N. (1979) Ceanothus of California: a gardeners guide. Pac. Hort. 40(2): 37-45.
Smith M.N. (1979) Ceanothus of California: a gardener's guide: 2. Pac. Hort. 40(3): 36-43.
Van Rensselaer M. & McMinn H.E. (1942) Ceanothus. Santa Barbara Botanic Garden, Santa Barbara: 308 p.