Pampas grass growing over the sidewalk

The neighbors across the street have huge and showy pampas grasses growing next to their driveway. I was not surprised to find its offspring on our side, on the edge of our sidewalk, growing more obtrusive every week. I cut it off at the base with a saw but it grew back more beautiful its green sword blades having sandpaper edges. I cut it down a second time and poured vinegar into the matted base, but it grew back again. After I cut it down a third time I poured a gallon of vinegar into it and the ground was dry so I hope the vinegar killed the roots so it’s finally done for.