I'm afraid you'll be in for more problems since sorrel will survive fires. I've posted a link for you which is a good read on this pest. I have it too and simply keep at it trying to get as much root as possible since they 'run'.

Mulching has helped in my case as well as improving the soil. More humous and less acidity really help. In our Hosta gardens they don't exist. The big difference is the soil quality.

Here is a link that might be useful: Sorrel.

one of these ought to do the trick.

{{gwi:532297}}