Same here ... the Bermuda grows by its roots underground, on top of the soil and also produces seeds. It comes from the yard next door. I don't like sprays but sometimes have to use them since they don't edge the fence line on their side. I made a "raised" bed with a kiddie pool and have not had problems with grass in it; however, it will sometimes dry out and that's a problem. The lasagna bed to the left of it has had some grass grow into it. I've had to use a growth inhibitor on occasion.
I do love lasagna gardening.
