Posted: 31/08/2015 at 10:02
If you are going to try weedkiller you need to crush the stems first. Either by walking on them or cruching up by hand. That helps to break the surface of the stems and lets the weedkiller in.
Possibly not an option for an established border, but I'm currently working on a plot about 25 x 15 ft which doesn't have any planting. I'm using a garden fork to get as deep as possible and going through each clump by hand to remove as much as I can. Our soil is light so, before this rain!, it was easy to crumble the soil off the MT and find roots left behind. I'm under no illusion that it will completely eradicate the problem but I will hopefully be able to keep regrowth under control then. It is a big job though.