I made several into a "container" of sorts. I did not clean them as you describe since they were already deep enough...put soil in, planted things... turned out OK for one instance, but for the others I had competition. It seems chipmunks or something was living down below, and they tossed everything, soil and plants, out. I tried replanting because, at first, I did not realize what was wrong. Eventually I gave up. Critters win almost every time. Double check to make sure nothing is living under the trunk before you make the effort to clean it out.

I saw someone do this on a tv show with a chain saw once. Never tried it myself.

nc rescue...good point thanks!
THat must have been baffling and maddening..you r right tho' those critters do win almost every time!

Now I have never tried this but I have heard of putting salt on the stump or in your case just in the center. Of course if that did work it may be a little more time consuming kinda like watching paint dry cause I am sure it would take some time for it to work.

I did this (with the help of my nephew) using a drill and a bit used to hollow out holes in wood. It took a little time, but we were able to successfully dig about 8 inches into a large oak stump, in order to plant wave petunias in it at my mom's house. It's beautiful now!

I had a stump planter for a few years. I took an axe to the top of a huge elm stump....only managed to hollow it to about 5 inches deep, but it was enough to plant a few cascading petunias.
The combination of the organisms in the soil and the watering caused the stump to rot out in about 5 years...which was the goal.
Put it was a pretty planter for a while.
Linda C

You might also want to consider if its close to the house, it could attract Carpenter ants and termites if you have them in your area.