when dirt is not dirt

my vegetable plants are still growing, green and pretty and I am continually teased with the possibility of a vegetable here & there but nothing has grown to fruition as of yet. Disappointing to be sure however I am not ready to through in the "yes I too can garden towel". I have plans to start a compost pike for next spring and hope to get the raised plot that must have been a garden at one time in our yard cleaned off this winter. In the meantime I bought a few mums already started for the flower planter out front that never quite managed to grow any of the flowers seeds planted. As I grabbed my potting soil I noticed in big letters on back "not for containers" has that been my problem all along I bought the wrong dirt?! who knew there was a right & wrong kind of dirt?