A commonly quoted Wiccan tradition holds that the ideal number of members for a coven is thirteen, though this is not held as a hard-and-fast rule.[30] Indeed, many U.S. covens are far smaller, though the membership may be augmented by unaffiliated Wiccans at "open" rituals. When covens grow beyond their ideal number of members, they often split (or "hive") into multiple covens, yet remain connected as a group. A grouping of multiple covens is known as a grove in many traditions