Almost half of our plot was covered in thick couch grass when we took it over, and as we didn't want to use any chemicals we covered areas over and then when it was weakened we dug it out as best we could. Two years on we have only a minimal area at the back now with couch grass. I am a great believer in getting something planted in as soon as you have a place clear, it doesn't matter if you still get pockets of it, you will gradually get shot of it the more it is cultivated. :) busy_lizzie