Not only oak barrels

Oak is certainly by very far the most popular wood to use for barrels, but it is not the only. EU has recently approved the mention on wine labels that the wine has been fermented or aged in wood other than oak. It is also permitted, though not required, to mention on the label the type of wood. In other words, you may in the future see on the label e.g. “aged in barrel” or even “fermented in chestnut wood” (or corresponding national wording). Journee-vinicole.com