What is the best way to kill alders and their root systems without affecting the groundwater? (I'm on a well).
Matanuska-Susitna Borough Alaska pesticides
It's a little late in the year to spray them. They have to be actively growing. I would mow them this year and spray them next spring when it's above 55 degrees and they are actively growing.
You can use Roundup per label as it does not affect groundwater (soil bacteria eats Roundup within 24 hours.)