What depth of drainage stones do I need in the bottom of a large planter box? Are there any recommended stones?
I think the practiceof placing stones in the bottoms of containers is no longer considered necessary. It might be best to choose a container that will allow for root growth, and one that has drainage holes in the bottom. Use a soil mix that has, in addition to organic matter (compost, etc.), sand, coarse grit, or some baked clay granules (Turface is one) for drainage.