frustratedearthmother
Sustainability Master
When I built mine, some years ago, we put a mix of bagged topsoil, compost and manure. One bit of advice - get the good stuff if you don't have any good soil or compost of your own to put in them. I bought stuff to fill some new tubs this year and didn't follow my own advice... I thought I could supplement with lots of manure from the barn. Didn't put enough in the first go round so I'm still supplementing and trying to find that right balance.