Old soil IN pots - okay to plant?

The old soil should be broken up/tilled to remove old root systems found in the pots. Mix the old soil with some new/bagged or right-out-out-of-nearby-ground soil to freshen a bit. A little vermiculite or coarse sand would help to aerate the old soil. Yes, plant your flowers in these pots with the reconditioned soil. Apply the same process with large raised beds. Hope this is helpful. Good Luck.