Mares tail is the biggest pain of a weed going. It will find it's way through anything even came up through our driveway which then need to be dug up and re-laid. The problem mares tail we had coming up between the house and the canal we have almost eradicated.

I hate weedkillers even the ones they say are safe but on this occasion we did use weedkiller (strongest one we could find!) left it until it looked dead, then we cleared it and then spent another couple of years pulling them up gently to ensure we got the whole thing. If any of the bits break off they seed themselves and then start growing again. Fingers crossed 9yrs on they have virtually gone now and for the last three years been growing tomatoes, lettuce, carrots, parsnips and cucumbers.

Good Luck and happy weeding!!