The casks in which whisky matures are made from a wide variety of oak species. Often the previous liquid held in a cask is cited when referring to a Single Malt Scotch Whisky’s maturation, e.g. matured in an Oloroso Sherry Cask, but the species of oak used to make the cask also has a profound effect on a Scotch Whisky’s final character.
When discussing the type of oak used in cask making, it can be misleading, as the wood is often referred to as European, American, French Oak, etc. These are used as a general geographic names, as opposed to the specific species of the wood. This is sometimes done for a number of reasons; not least many oak trees are prone to hybridisation. However, there are some species that are used most commonly in the production of whisky casks, which we have been outlined here. Each species will have its own effect on the flavour of a whisky.
The most common species of American White Oak used in the production of whisky casks is Quercus Alba, so called due to its paler appearance compared to European Oaks. American White Oak is by far the most commonly used in cask production, due to its abundance. It is invariably used to create barrels which mature American Bourbon Whisky, that are then shipped to Scotland to mature Scotch Whisky.
Quercus Alba has a typically much softer and more mellow influence on whisky than many of the European Oaks and can impart a taste and aroma of caramel, coconut, honey and vanilla.
The above shows the grain and pale characteristics of Quercus Alba (American White Oak).
The most common species of European Oak used are Quercus Robur and Quercus Petraea. However, far fewer casks are made from European Oak than from American White Oak, as the wood takes longer to grow and prepare for cooperage. Quercus Robur grows more commonly in the forest regions of Northern Spain and Portugal and is most frequently used in the production of Sherry casks. Quercus Petraea is more prolific in the forest regions of France and is generally preferred for the construction of Wine Barrique Casks.
Quercus Robur has a strong character and can impart a very dark colour to whisky. It will often have strong, punchy influences, such as spices (nutmeg, cinnamon), dried fruits (sultanas, prunes) and citrus peel.
Quercus Petrea has a more subtle influence compared to Quercus Robur, with notes of vanilla, pepper, and more delicate spices and dried fruits.
Quercus Robur is distinctively darker than the more commonly used Quercus Alba (American White Oak) and imparts a much darker appearance to whisky.