List of Quercus species
The genus "Quercus" (oak) contains over 500 species, some of which are listed here. The genus, as is the case with many large genera, is divided into subgenera and sections. Legend. Species with evergreen foliage ("live oaks") are tagged '#'. Species in the genus have been recategorized between deciduous and evergreen on numerous occasions, although this does not necessarily mean that species in the two groups are closely related. Subgenus "Quercus". Section "Quercus". The white oaks (synonym sect. "Lepidobalanus" or "Leucobalanus"). Europe, Asia, north Africa, North America. Styles short; acorns mature in 6 months, sweet or slightly  bitter, inside of acorn shell hairless. Section "Ponticae". Western Asia and Western North America, produces catkins up to 10cm long, fruit matures annually. Section "Mesobalanus". Europe, Asia, north Africa. Styles long; acorns mature in 6 months, bitter, inside of acorn shell hairless (closely related to sect. "Quercus" and sometimes included in it). Section "Cerris". Europe, Asia, north Africa. Styles long; acorns mature in 18 months, very bitter, inside of acorn shell hairless or slightly hairy. Section "Protobalanus". The intermediate oaks. Southwest USA and northwest Mexico. Styles short, acorns mature in 18 months, very bitter, inside of acorn shell woolly . Section "Lobatae". The red oaks (synonym sect. "Erythrobalanus"). North, Central and South America. Styles long, acorns mature in 18 months(in most species), very bitter, inside of acorn shell woolly. Subgenus "Cyclobalanopsis". The ring-cupped oaks (synonym genus "Cyclobalanopsis"). Eastern and southeastern Asia. They are distinct from subgenus "Quercus" in that they have acorns with distinctive cups bearing concrescent rings of scales; they commonly also have densely clustered acorns, though this does not apply to all of the species. About 150 species.