There are two ways to trim and edge turfgrass around sidewalks, flower beds, trees, buildings, etc. You can trim the turfgrass mechanically with a string trimmer and/or an edger, or you can use a non-selective herbicide such as glyphosate (Roundup® and similar chemicals).
Turfgrasses grow fast and aggressively in the South. If not edged back regularly, Southern turf will grow right over sidewalks, driveways, flower beds, etc.
The LSU AgCenter and the LSU College of Agriculture