Brambles aren't too hard to clear. They look worse than they are. Keep cutting them back a bit at a time 'til you find the roots and dig 'em up. It might take a couple of seasons but they do give up. If you can use glyphosate without damaging other stuff, that will help kill the roots. They have the very strange advantage that very little else grows near them, so when you clear the brambles you have cleanish ground.

Couch grass is something else. And marestail is a nightmare.

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