As its name implies, a perennial is a plant that comes back year after year. Some are referred to as “half hardy” or “tender.” This means that they won’t survive frost and must be moved indoors during the winter.
In the case of Salvias, a sunny greenhouse is the best indoor location for wintering over. Or, you may choose to plant the Salvia as an outdoor annual. Rapid growth and long bloom times make this an acceptable option.
Keep in mind that a perennial may be hardy in one region but not another. It is wise to know the highs and lows of local temperatures and to make plans and choices accordingly.