Have you considered a crane ?
It sounds like the planter has no bottom. Is there any reason why the planter cannot be lifted off the trunk ? I have done several that way.
Once you have it in the air (or moved), the stump should be easy to deal with.
If you MUST cut it up with a chainsaw: buy a short bar, and put some carbide tipped chain on it. Slower cutting than normal chain, it will breeze through dirt and at least a little rock without getting dull. Quite expensive though, and very tricky to get sharpened !
It sounds like the planter has no bottom. Is there any reason why the planter cannot be lifted off the trunk ? I have done several that way.
Once you have it in the air (or moved), the stump should be easy to deal with.
If you MUST cut it up with a chainsaw: buy a short bar, and put some carbide tipped chain on it. Slower cutting than normal chain, it will breeze through dirt and at least a little rock without getting dull. Quite expensive though, and very tricky to get sharpened !