Q.Does glyphosate transfer from couch grass to surrounding good grass?
Big problem with couch grass invading lawn. I thought if I painted a few leaves with glyphosate it will kill it – but will it transfer through the roots to other grass that it is displacing ?

Certified GKH Gardening Expert
Whatever does make it to the soil will be such a small amount that it won't really harm anything. Now, if you are spraying, then the stuff won't be selective. It will kill almost anything in its path.
Most people have a larger area to kill couch grass and must spray good grass and couch grass. Once the couch grass is eradicated, they must reestablish good grass.