I should add that my planters are on a drip system hooked up to a fertilizer unit that gives a small dose with every watering. I also put time-released fertilizer in each pot and earthworm castings. None of that helps the potting mix that is filled with last year's roots though. If you can't break the ball of potting mix apart because the roots are holding it together that well, I don't think you can reuse it unless you compost it.
