Three years ago, I had to cut down a 30 year old olive tree. It was all burled and knurled at the foot of the truck. I must have sprayed the stump and the regularly appearing shoots with Roundup, at least once a month. I covered it up with dirt and a big boulder. No luck, the new shoots keep sprouting out of the old stump.
Any suggestions for bringing about its demise, or do I give up and let this thing grow into an olive bush?