Question
We cut down a very large willow last year and left a 6 foot tall stump.
Are the roots still active? Our neighbor said the roots are growing into his house and causing damage to the foundation. He has water coming in now, but none before the tree was cut. We would like to kill the stump ourselves. Do you have any advise?

Answer

They are fairly easy to kill. Buy a herbicide called Roundup. It will not take much so get the smallest container you can find. Cut the  stump again and immediately paint the freshly cut stump with Roundup. The herbicide will be taken up by the tree stump and transported to the root system and kill the tree and its roots. Roundup is a herbicide that will kill almost any green plant so when you paint the stump do not get it on any other plant not wanted to be killed. The active ingredient in Roundup is Glyphosate. You can find and use other name herbicide products with Glyphosate and these maybe less expensive than Roundup.

The reason to cut the stump is to give a fresh surface for the chemical to enter. Tree roots will not damage a foundation unless there is water present and a crack is in the foundation for the root to enter. Willow roots seek water and if there was a water source they would grow toward it. The herbicide will solve the roots problem.