Flexible plastic edging can help visually differentiate your flowerbeds from your lawn. Although cutting a trough between your flowerbeds and your lawn can slow grass encroachment, plastic edging can create a barrier over which the grass cannot grow. Proper installation of plastic edging is important in preventing frost-heave damage and preventing damage from everyday activities like lawn-mowing. Properly installing plastic lawn edging, which should be commercial-grade and at least 5 1/2 inches deep, is not difficult.
Cut the edge of your bed into the grass with a sharp, flat shovel.
Peel back the grass over your intended garden bed with a shovel. Remove the grass.
Dig down at least 6 inches into the soil in your garden beds. If you are planting deep-rooted plants, you may want to go even deeper. The 8-inch recommendation is for the benefit of the edging, not your plants.
Cut any roots that might interfere with your edging.
Lay your edging loosely around your bed. Make sure that the upward V on the bottom of the edging faces inward. The loose soil will fill that V and help hold the edging in place.
Connect edging pieces to fit longer runs, using connectors that usually come with spike kits.
Trim any excess edging, using a utility knife.
Set the edging so that only the top 1/2 of the circular portion of the edging is visible above the surface.
Move loose soil under the V-shaped portion at the bottom of the edging. As you feel it fill, the edging will have a tendency to rise. Press the edging down into this loose soil. Do not cover the entire surface on the inside of the edging yet.
Secure the edging with spikes or stakes. Drive the spikes through the edging from the bed side of the edging into the soil on the lawn side of your flowerbeds.
Backfill along the bed side until the soil is level with the grass on the other side. Continue setting the edging base along the edging run.