Copper sulphate has been used for centuries as seed treatment and also to treat fire blight in dormant trees. While not a common practice, copper sulphate can be used as a chemical agent to burn out a tree stump if other methods of tree stump removal have not worked, such as digging, rotting or grinding out a stump. You can use copper sulphate to burn out a tree stump, which you can then remove from your landscape.
Dig out as much of the tree stump as you can before applying any chemical treatments to it. If you can, grind away the top of the stump with a stump grinder, or use a saw or chain saw to cut down the stump as close to the ground as possible.
Drill several 1-inch holes into the stump and space the holes approximately one inch from each other. Try to drill the holes at a 45-degree angle, and drill down 12 inches deep.
Insert copper sulphate into the holes and pack it tightly. Do not touch the copper sulphate with your bare hands. Use the end of a hammer or long stick to pack the copper sulphate into the stump holes.
Cover the holes with a plastic garbage can lid and then weigh the lid down with bricks or concrete blocks. Do not use a metal lid, as the copper sulphate will corrode the lid.
Wait several weeks. The copper sulphate will not dissolve the tree stump. It will merely speed up the rotting. You may need to add additional copper sulphate after a few weeks and repeat the covering process.
Copper sulphate is a very caustic chemical. It can cause sickness and injury if inhaled or if it comes in contact with your skin. Do not use copper sulphate without wearing a protective face mask, eyewear and gloves. Also, do not use copper sulphate if your tree stump is near a water source or if you have children or domestic animals that may accidentally come into contact with the tree stump. In addition to killing your tree stump, the copper sulphate that comes into contact with the surrounding landscape will also kill grass, plants and other trees.