Specialty Gardening: Best soil/suggestions for large sinking planters, 1 by palmbob

palmbob wrote:
The whole back yard is planters (mostly to keep dogs out of plants) and filled with potting soil I had trucked in... but now that it's raining 6 months later I have noticed the process of 'sinkage' is more pronounced. I will need to, at some point, dig up all the plants and refill the boxes with more soil. I would like to do this only once. Any suggestions? I have a lot of rocks ready (hoping they will sink less, or at least compact less) and am thinking about getting a lot of pumice... but dont want to compromise plant nutrition or have them dry out too much in summer heat. Need a good compromise. What would you recommend?