What sort of weeds? Most weeds will die with a season's cutting, including many grasses. The couch should go that way, if you exterminate rhizomes which spread beyond the lawn. Rosette weeds need to be cut once a month or so for a season. If you cut the grass short, they lie down below the mower blades, but if you let it grow between mowings, they rise off the ground and become vulnerable.
