Edging keeps a loose-fill garden path neat. Edging material can tie design elements from your home -- brick, wood or stone -- into the landscape or be strictly utilitarian. The type of edging you choose for your mulch or gravel garden path will depend not only on your budget, but also on the shape of the path. Treated timber or brick can be used to keep straight paths in check, while small pieces of stone or flexible plastic, wood or metal edging can be used for curving paths. Whichever material you choose to edge your path, preparation and installation is similar.
Cut into the soil with your flat-back spade at the division between the turf and the path at least 2.5 cm (1 inch) deeper than the bed of your path, which should be about 15 cm (6 inches) deep. Put your shovel in with its back at the turf and push straight down to make a flat edge.
Make the same cut all the way down the length of both sides of the path.
Cut a channel with your flat-edge shovel to match the depth of your edging material, approximately 5 cm (2 inches) away from and parallel to the first set of cuts, if using bricks, stone or landscape timber, and dig it out so the bottom of the trench is relatively flat. If you are using plastic edging, push your shovel forward from the first edge cut to open a V-shaped trench.
Fit your edging material into the trenches on each side of the path. Stone, brick or timber should be lined up so joints are touching or positioned as closely as possible. Push plastic edging down into the trench. The tops of all types of edging should be aligned with or an inch above the surface of the grass.
Drive in 20 to 25 cm (8 to 10 inch) metal timber spikes with a hammer every few feet along the length of plastic or wooden edging. Butt the spikes up against the edging material on the path side to hold the edging in place against the turf. Drive the top of the spike in so it rests at least 2.5 cm (1 inch) below the surface of the filled path. Install extra spikes along any curves in plastic edging.
Backfill soil with your spade along the base of edging material so it is secure in its channel. Fill the path with your chosen material until it is about 2.5 cm (1 inch) below the top of the edging material.
Standard homeowner-grade plastic edging is 7.5 to 10 cm (3 to 5 inches) deep. Commercial-grade edging, which is 15 to 20 cm (6 to 8 inches) deep, is recommended by the Sustainable Urban Landscape Information Series, as it stands up better to changes in weather and other harsh conditions.
Timber or plastic edging that is not staked may move out of place over time due to frost heaving.