Filler for large pots
I am about two weeks from planting annuals in fairly large containers...2' tall X 30" dia. Some larger, some a little smaller. The point is, they take a lot of soil or 5-1-1, etc. for a relatively short growing season. I am told the medium needs to be replaced every year. Even in the best medium, I can't imagine roots of the annuals getting to the bottom of the pot. Is there a good filler for the bottom of the pots that I can spread on the mulched area of my yard and use 5-1-1 for the top foot...or maybe just pine mulch or unscreened 5-1-1?