From an oenological point of view, there are two principal groups of oak:
French oak
This encompasses two great production zones, with differentiated species:
- Quercus robur or Quercus pedunculata. This is the so-called Limousin oak. These trees grow in very fertile soils and are wide yet short with a large diameter trunk. The wide grained, very porous wood (much separation between the growth rings) facilitates interchanges with the surrounding environment (evaporation and oxidation). It has much tannin (55 gr./kg) and aromas reminiscent of toasted almond and caramel (hydroxymethyl - furfural). It is used for ageing brandies (Cognac and Armagnac).
- Quercus sessils or Quercus petraea. This is most abundant in the woods of Allier, Nevers and Tronçais. It prefers poor, sandy soils, giving taller trees with a smaller diameter trunk and finer grain. It has a lower tanning content (45 gr./kg) and is ideal for wine ageing. Its aromatic notes are drier, more serious and spicy (this wood is rich in eugenol which has a clove aroma). Evaporation is lower than for the Limousin oak.
American oak
This principally pertains to the species Quercus alba or white oak. It is spread through the states of Ohio, Missouri, Virginia, Wisconsin, Illinois and Iowa. This oak has a strong texture (density) and fine grain. Although it has the lowest tannin content (35 gr./kg) it is rich in aldehydes (vanilla aroma) and lactones (coconut aroma). However, it has little Eugenol (clove aroma) and therefore imparts a stronger "boisé" or woodiness than the French oak, although with a lower tannin content. It is not a 2nd class oak, but its use must be adapted to a well defined wine style.