The Glenrothes uses a combination of Quercus Alba (or American oak) and Quercus Robur (European or Spanish oak) so they enjoy the best of both worlds. Quercus Alba brings coconut and vanilla flavours to the whisky as well as some sweetness. The spiciness, tannins and dried fruit character of The Glenrothes comes from Quercus Robur.
The rarest and most expensive casks of all are those of Quercus Robur, grown in Northern Spain and then seasoned in Jerez with Oloroso sherry. They are prized for the great richness they impart on the whisky maturing within.
The Glenrothes Robur Reserve benefits from a greater proportion of Spanish oak first fill sherry cask influence, making it spicy, fruity, sweet and delicious.