If you're planning to mulch your garden, edging will help keep it in place. Plastic edging is the most economical type and the easiest to work with, but it won't give you the sharpness or well-defined edges that a stone, brick, or wood edging will.
Step 1 - Create the Line for the Edging
If you don't already have a defined line where you're planning to install your plastic edging, create one. Lay rope in a loose shape, including the curves of landscaping, before you start digging. Once you have a layout, follow the line of the rope with spray paint to mark the grass or ground beneath it. Remove the rope.
If you don't want to paint your lawn, lay out a garden hose and let it sit in place for a few days. The weight of the hose will leave an indentation in the grass once you move it. Cut your trench the same day if possible, or replace the hose.
Step 2 - Create a Trench for the Edging
Use a straight-edged hoe, spade, or tree dibble to remove the sod or earth marked by your line. Your lawn edging is vertical, so make your cuts straight downward (vertical). You'll want to remove the same number of inches of sod below the level of the grass roots as the thickness of your edging. If your edging is 4-inches wide, remove that much plus another 2-inches.
Step 3 - Unroll and Install Your Plastic Edging
Measure and unroll your plastic lawn edging. Cut it to length, trying not to splice or piece the edges unless you have to. Since edging comes wound into a tight circle for packing, it will have a curl to it when you unroll it.
Place the circle so that the outside of the curl faces the area you plan to mulch. Going against the curl of the edging this way, slide it into the trench you've dug. The top of the edging should be almost buried, but still visible once you backfill the trench-about ½-inch above the ground. It should be level with the growing edge of the grass.
Step 4 - Install Lawn Edging Stakes (Where Needed)
If you have a really wavy or curvy edge, you may need to add edging stakes to hold the curve. Edging stakes go in horizontally, not vertically. Hammer the stakes through the edging, just above the reinforcement strip, and then into the soil under the lawn. Tamp down the soil, compacting it with your foot or by watering with a hose.
If installed correctly, you should be able to mow right over the edging by placing one of your lawn mower wheels against the plastic.
Step 5 - Add Mulch
Once your edging is in place, add your mulch. For best results, apply to a depth of 3 to 6 inches for retaining moisture and keeping your plants healthy, protected, and happy.