You'll definitely need one that is balanced and slow released. The soils in a pot end up getting washed pretty regularly, given their porousity. Think of it like pouring water onto the top of a sponge- some stays, some goes through, and it dries out shortly. This has a tendency to wash out a lot of the nutrients. If you use a lot of fertilizer you run the risk of accumulating salts, which can cause damage. Drum roll please... in Jamaica... Dave & I saw a lot of this even though they were in clay. They fed their nutrients through an irrigation system which they ran pretty frequently. Ater a few weeks of application and evaporation, there were places where the salts build up was obvious. -Jim C Mild to Wild