There are several ways to remove unwanted tree stumps. You can dig them up, have a professional buzz them up with a grinder, pull them up with a backhoe, burn them, or use commercial preparations or other chemicals to speed up their decomposition.
When to Use Chemicals
Some trees have extensive root systems and a tap root that makes it difficult to dig up a stump or pull it out using a backhoe. A grinder will flatten a stump to the ground but does nothing to get rid of the roots. There are often legal restrictions against burning. Letting a stump decay naturally can take 5 to 10 years. This is when you consider using chemicals to speed up the decomposition.
How Chemicals Work
Chemicals accelerate the rotting of the stump.This method requires patience because it can take weeks for the stump to break down.
Chemicals that are available commercially to degrade stumps include sulphuric acid, nitric acid, and potassium nitrate, also called saltpetre. The acids eat the wood. Potassium nitrate, used in explosives and as fertiliser, feeds the fungi that causes the wood to rot. Any fertiliser that is high in nitrogen can also nourish the fungi.
How to Apply
The stump should be dead for at least a year. Do not attempt to use chemicals on freshly cut stumps.
Use a chain saw to cut the stump as close to the ground as possible. You should be left with a low, flat surface.
Use a one-inch wide spade bit to drill holes three to four inches from the edge of the stump. These holes should be about 6 inches apart and 12 inches deep.
On the outside of the stump about three or four inches from the rim, drill holes at a 45-degree, downward angle to intersect with the holes that you drilled on top of the stump. These holes provide vents for the chemical action and speed the decomposition.
Pour about a half-cup of sulphuric acid, nitric acid or potassium nitrate into each of the holes that you drilled on top. Fill them with water.
It will take from a month to six weeks for the stump to decompose. You might have to reapply the chemicals.
Once the stump is decomposed, you should burn it.
Always follow the directions on the label of any commercial stump-removing chemical.
Using Sodium Hydroxide
You can usually find sodium hydroxide, also called caustic soda or lye, at a store that sells hardware or paint.
Pour a solution of one part caustic soda and two parts of water over the tree stump. You might have to do this several times before the stump is removed.
Killing the Roots
If your stump is not yet dead and you want to kill the roots, burn the top or grind it flat to the ground. Cover the top with a drying agent, either Epsom salt, magnesium sulphate, or rock salt (sodium chloride), and cover it with dirt.
Sulphuric acid, nitric acid and sodium hydroxide are highly toxic and can cause noxious fumes and severe burns. Use rubber gloves to protect your hands and goggles to protect your eyes. Do not inhale the fumes. Use caution when using these chemicals and keep children and animals at a safe distance.