Soil depth can very according to what the soil is composed of and how often you will be watering it. So, it can be anywhere from say 2" and up to the depth of my raised beds which are about 16" deep.
There are semps planted in tiny pinch pots/hypertufa with maybe an inch of soil. Of course these will need more attention to watering in the dry season. I find that soil is wasted for semps in big deep pot, so really like the idea of adding light weight items to the pot before adding soil. Crumpled bubble wrap, milk jugs, etc, all work well.
This is also a time to think about making your potting mix fast draining. If you are using large containers and filling them with potting soil, they make retain way to much moisture long term. There just won't be enough roots to take up the moisture down deeper in the big pots.
Maybe some one can add more to this?
