Q: I recently cut down a thirty-year-old wisteria vine in my back yard. Now the whole stump is covered in new growth. Is there anything I can use to stop the growth, kill the root system, etc.?
A: Remove the existing new growth. Then use a machete or small hatchet to chop into the top and sides of the stump. Use a foam paintbrush to dribble herbicide into the cuts. Look for a weed killer that contains both glyphosate (click for sources) and triclopyr (click for sources) as the active ingredients. Both of these chemicals inhibit resprouting but the combination is better than either one alone. That said, you’ll probably see lots of root sprouts popping up many feet from the main trunk. You’ll have to be persistent at removing leaves any time you see them in order to eventually starve the roots to death.