Question: If I used copper sulfate pentahydrate in my septic system that might have killed the ornamental pear tree, is it still okay to use as mulch or will there be residual root killer in the mulch that would end up killing my other plants too? I could not manually get all the roots out of the lateral lines so I was told to use the copper sulfate. Are there alternatives?
Answer: Copper sulfate products are extremely toxic in many ways. They have been banned in several states and should be taken off the market. Nothing can be put into pipes that will kill the roots that are causing problems without hurting the trees and shrubs that are the culprits and damaging the soil. The only good solution is to have the lines replaced so they are solid and impenetrable so roots can't get in. Sorry - I know it will be expensive. I'm just the messenger.