The French oak forests constitute one of the largest oak-growing regions of Europe. The main forest regions are controlled and auctioned by the French government to assure availability and quality. Five primary forests used for wine barrel production are Allier, Limousin, Nevers, Troncais and Vosges.
Forest of origin is a significant factor in the choice of oak in that the terroir and climate of a given region affect, among other things, the density or tightness of grain in the wood. A tighter grain not only means a less porous wood, which ensures a watertight barrel, but releases oak flavour to the wine more slowly with characteristics of vanilla, spice and butter. Leeuwin Estate for example uses fine-grained woods from the Allier and Troncais for their Art Series chardonnay.
By contrast, tough, coarse, loosely-grained wood, such as oak from Limousin, imparts strong flavours more aggressively and is usually less suitable for wine barrels.
An individually-named oak-only forest within the Allier region, of over 10,000 hectares, the average age of trees is 250 years. Tronçais is significant not only for the desirable characteristics of its oak but due to history as well. Tronçais was one of many large tracts of forest planted in the 17th century under Loius XIV to provide oak for the French navy. The oak species is Quercus robur exclusively. In deep, rich, loamy soil, Tronçais oak grows to great height. The excellent growing conditions make for very rapid vertical growth and minimal lateral expansion, resulting in an extremely tight grain. Subtle oak flavours make Tronçais well suited for prolonged barrel aging.
A bit more trivia of Troncais
List of classified trees within the forest:
Square Oak (circumference: 6.44 m, age: 370 years)
Oak Emile Guillaumin (circ. : 3.80 m, age: 350 years)
Oak Jacques Knight (circ. : 4.70 m, age: 370 years)
Twin Oaks (circ. : 4,10 and 4.50 m, age: 400 years)
Oak Louis-Philippe (circ. : 4.60 m, age: 350 years)
Oak Montaloyer (circ. 5.48 m, age: 400 years)
Oak of Resistance (circ. : 3.60 m, age: 350 years)
Oak Saint-Louis (circ. : 6 m, age: 450 years)
Oak Sentinel (circ. 6.55 m, age: 475 years)
Oak Stebbing (circ. 4.60 m, age: 350 years)