You can add slow release pellets of food or, if you prefer to be organique, mix some pelleted chicken, cow and/or horse manure at potting up time. An occasional liquid feed of rose or tomato fertiliser will do wonders too.
Stand the pot in a saucer for the summer so it doesn't drain all its water away but make sure it's raised on feet in winter so excess moisture can drain and avoid freezing the roots to death.