There's grass and then there's GRASS
Do you have
lawn? Near the garden? Any idea if it's 'running' or 'clumping' grass?
Running grass can be a nightmare. I suggest digging around in the lawn and new bed. See any horizontal, fat, pale roots?
If so, stop! Cutting just encourages running varieties
I think grass is a total pain (but I have no HOA, kids, or dogs...)