In America, the species of oak typically used is the Quercus alba which is a white oak species that is characterized by its relatively fast growth, wider grains and lower wood tannins. It is found in most of the Eastern United States.
In France, both the Quercus robur (common oak) and Quercus petraea (white oak) are considered apt for wine making; however, the latter is considered far superior for its finer grain and richer contribution of aromatic components. French oak typically comes from one or more primary forests: Allier, Limousin, Nevers, Tronçais and Vosges. The wood from each of these forests has slightly different characteristics.
Prior to the Russian Revolution, Quercus petraea oak from Hungary was the most highly sought after wood for French winemaking. The trees in the Hungarian Zemplén Mountains grow more slowly and smaller in the volcanic soil, creating fine tight grain which sequentially lends itself to a very delicate extraction. The hemicellulose in the Hungarian oak breaks down more easily, and conveys an exceptional selection of toasted, vanilla, sugary, woody, spicy and caramel-like flavors – imparting these aromas with less intensity, and more slowly than American or French oak.
Many winemakers favor the softer, smoother, creamier texture that Hungarian oak offers their wines.
Barrels are constructed in cooperages. The traditional method of European coopers has been to hand-split the oak into staves (or strips) along the grain. After the oak is split, it is allowed to “season” or dry outdoors while exposed to the elements. This process can take anywhere from 10 to 36 months during which time the harshest tannins from the wood are leached out. These tannins are visible as dark gray and black residue left on the ground once the staves are removed. The longer the wood is allowed to season the softer the potential wine stored in the barrels may be but this can add substantially to the cost of the barrel. In some American cooperage the wood is dried in a kiln instead of outdoor seasoning. While this method is much faster, it does not soften the tannins quite as much as outdoor seasoning.