French oak, American oak and the rest

The usual shorthand — French oak gives subtle spice, American oak gives coconut and vanilla — has enough truth in it to be durable and not enough to be reliable.

What actually reaches the wine depends on at least five variables besides species, and any of them can outweigh it.

The main species are Quercus robur and Quercus petraea in Europe and Quercus alba in North America. Q. alba is generally reported higher in oak lactones, which are associated with coconut and sweet wood characters.

Grain tightness varies with growing conditions and is often more predictive than country of origin. Slow-grown tight-grained oak yields its compounds more slowly whatever forest it came from.

Preparation differs by tradition. European oak is typically split rather than sawn and air-seasoned outdoors for two to three years, which leaches and modifies compounds before the barrel is made. American oak has more often been kiln-dried and sawn, though air-seasoning is now widely used for premium barrels.

Toasting is applied by the cooper and is a large variable in its own right, changing which compounds are formed and in what proportion.

Hungarian, Slavonian, Caucasian and Austrian oak are all used, and Slavonian oak in large formats is traditional for Barolo, Chianti and Rioja.

The consequence is that "French oak" describes a purchasing decision, not a flavour. Two French barrels from different coopers with different toasts will differ more from each other than either differs from some American ones.