There are many, many kinds of oak tree—it’s a remarkably widespread and diverse genus. Hundreds of species of this long-lived hardwood grow around the world, but especially in the forests of Asia, Europe, and North America. In the United States alone, there are almost 100 species of oak.
Despite this huge range and diversity, coopers use only a few species of the Quercus genus to make barrels, using lumber from trees grown in relatively small areas.
That’s partly because many species of oak are poorly suited for coopering. Some are simply too short, too thin, or too twisted. Others have pores that are too wide, leading to leakage or an enormous loss to the angels. Still other oak species can be used to make tight barrels, but they’re so full of tannins that a spirit aged in them becomes unpleasant and bitter.