u/Haunting-Marzipan-25

So I have a very well established thicket of Japanese knotweed on an adjacent piece of land next to mine. It is early summer here in Scandinavia, and it is already 3 meters tall in some places. I know I should wait for ‘the window’ before starting herbicide treatment, but would an early treatment to stem the growth of the existing stems be in order?

Nevertheless, I have a huge job ahead of me

Pic for reference