In early spring and early fall we cut bed edges
Some gardens have hard edges" such as vertically installed root
barriers (black polyvinyl strips are common). We prefer a cut edge
and maintain it this way.
It might seem like too much to do but this bed edge, 100 linear
feet, took only one hour to cut and clean. In doing it we weeded 18
inches into the bed all around. That eliminated the worst weeds
right where they start, and the effect lasts until fall.