Agnes is an odd species name for this small evergreen salvia. It hails from Mexico and is very similar to salvia lavanduloides but not quite the same. Agnes is paler blue and appears to be shorter in growth, about 80cm, but they flower about the same time, autumn winter or longer. Unfortunately they are both a bit frost tender which makes them less useful to inland gardeners.
An open, sunny position is probably preferable.
It is a good plant for pots and can be cut back after flowering to bring on a new flush. It seeds and can be grown from them or cuttings.