Styles are short the acorns mature in 18 months and taste very bitter. Protobalanus, the canyon live oak and its relatives, in the southwestern United States and northwest Mexico. The leaves typically have sharp lobe tips, with spiny bristles at the lobe. The actual nut is encased in a thin, clinging, papery skin. The inside of the acorn shell appears woolly. Styles are long the acorns mature in 18 months and taste very bitter. Lobatae (synonym Erythrobalanus), the red oaks of North America, Central America and northern South America.

( September 2021) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources in this section. This section needs additional citations for verification. The subgenus division supports the evolutionary diversification of oaks among two distinct clades: the Old World clade (subgenus Cerris), including oaks that diversified in Eurasia and the New World clade (subgenus Quercus), oaks that diversified mainly in the Americas. Section Ilex – ilex oaks of tropical and subtropical Eurasia and North Africa.

Section Cerris – cerris oaks of subtropical and temperate Eurasia and North Africa.

Section Cyclobalanopsis – cycle-cup oaks of East Asia.

Subgenus Cerris – the Old World clade (or mid-latitude clade), exclusively native to Eurasia.

Section Quercus – white oaks from North America and Eurasia.

Section Virentes – American southern live oaks.

Section Ponticae – with a disjoint distribution between western Eurasia and western North America.

Section Protobalanus – North American intermediate oaks.

Section Lobatae – North American red oaks.

Subgenus Quercus – the New World clade (or high-latitude clade), mostly native to North America.

The genus was divided into two subgenera and eight sections:

The live oaks are distinguished for being evergreen, but are not a distinct group and instead are dispersed across the genus.Ī 2017 classification of Quercus was based on multiple molecular phylogenetic studies and data, mainly originating between 20. The acorns and leaves contain tannic acid, which helps to guard against fungi and insects. The fruit is a nut called an acorn or oak nut borne in a cup-like structure known as a cupule each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on the species. In spring, a single oak tree produces both staminate ('male') flowers (in the form of catkins) and small pistillate ('female') flowers, meaning that the trees are monoecious. Many deciduous species are marcescent, not dropping dead leaves until spring. Oaks have spirally arranged leaves, with lobate margins in many species some have serrated leaves or entire leaves with smooth margins. Solitary oak, the Netherlands The leaves of a young oak Pubescent oak tree in four seasons, Zmajevac, Fruška Gora, Serbia Description The second greatest area of oak diversity is China, with approximately 100 species. North America has the largest number of oak species, with approximately 160 species in Mexico, of which 109 are endemic and about 90 in the United States. The genus Quercus is native to the Northern Hemisphere and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. The common name 'oak' also appears in the names of species in related genera, notably Lithocarpus (stone oaks), as well as in those of unrelated species such as Grevillea robusta (silky oaks) and the Casuarinaceae (she-oaks). There are approximately 500 extant species of oaks. Protobalanus (Trelease) O.SchwarzĪn oak is a tree or shrub in the genus Quercus ( / ˈ k w ɜːr k ə s/ Latin 'oak tree') of the beech family, Fagaceae. Possible Paleocene & Late Cretaceous records

Acorn tree life cycle