This is a very simple object that will prevent a Mr Stacky vertical garden from sinking into the ground. 

I followed the instructions on their website and drove a ¾" diameter bit of electrical conduit into the ground about 30" deep. Then over the exposed conduit, I slipped about 1 foot of 1" PVC pipe, a 1" PVC connector, and then about 5 more feet of PVC pipe. Once this was in place I put on the pots, but I noticed that they were sinking into the ground a bit more than I wanted.

So I made this shape that would fit over the electrical conduit and spread out the downward force of PVC pipes a bit. It's nothing fancy and there probably is something that would do this already in the plumbing aisle of the hardware store, but I didn't feel like going there and the printer was idle, so I made a couple of these things and it looks like they work just fine.