What is the strongest weed killer available to stop weeds from growing back? I am going to lay a few flagstones and don't want weeds growing through them.
Certified GKH Gardening Expert
I would actually recommend black or clear plastic. Pin it down over the area and let the sun do the work. It will cook the soil and will not only kill the weeds, but their seeds as well. You can also lay the flagstones on top of this with a layer of sand.