Original: The Japanese Camellia - often simply called "the camellia" - is the most prominent species in cultivation, with over 2,000 named cultivars. Next are C. reticulata with over 400 named cultivars, and the Christmas Camellia with over 300 named cultivars.
Simplified: Camellia japonica (often simply called Camellia) is the most prominent species in cultivation, with over 2,000 named cultivars; next are C. reticulata, with over 400 named cultivars, and C. sasanqua, with over 300 named cultivars.