Border spades are the secret to achieving perfectly straight border edges along flower beds and other boundaries in the garden. Spade blades are perfectly flat and meet the shaft without an angle, while shovels have angled, dished blades for scooping soil. The spade handle at the end of the shaft makes it much easier to cut borders. Border spades and digging spades are nearly identical, but the shafts and blades of border spades are much shorter. A simple trench is all that's needed for a border, but you can add stones or polyvinyl strips to the trench to get the look you want.
Lay rope or garden hoses on the ground to mark the design for your edging. You can use border spades to create curved edging, but the cuts won't be as crisp as with straight edges. Lay a second series of ropes or garden hoses parallel to the first to outline the width for the border. A 6-inch-wide trench works best for trench edging; polyvinyl edging requires a trench about 4 inches wide to allow working room; the trench for stone and brick edging should be a few inches wider than the stones or bricks.
Spray landscaping spray paint -- an environmentally safe, chalk-based paint -- along the ropes or hoses to transfer the outline to the ground. Remove the ropes or hoses.
Measure from the tip of the blade to the desired depth for the border. Apply a piece of tape to mark the blade to the correct depth. Trench borders should be about 6 inches deep; plastic edging should be the same depth as the edging strips; stone and brick edging depth depends whether you want to set the materials all the way into the ground or only bury the stones or bricks halfway. While this step is optional, the tape makes it easy to achieve a uniform depth throughout the border.
Stand the border spade upright at one end of the outside sprayed border line. Grip the handle with your dominant hand and place your other hand on the shaft.
Step down on the foot peg to push the blade straight down into the soil to the desired depth for the border. If you used tape to mark the depth, push the blade into the ground up to the bottom of the tape.
Pull the blade out of the ground and reposition it directly beside the first cut. Push the blade down to the desired depth. Repeat this process until you reach the end of the outer sprayed line.
Reposition the blade at one end of the sprayed line along the inside edge of the border. Push the spade down into the soil and pull the handle toward you, using leverage to pry up the soil between the inside painted line and the previously cut painted line. Repeat this process along the length of the inside painted line.
Remove all remaining soil between the two cut lines, using a shovel with a dished blade, if needed. Add edging material or drag mulch from the flower bed into the trench at a 45-degree angle. If the trench forms a square, the mulch should extend diagonally from the top corner closest to the flower bed to the bottom corner on the opposite side of the trench.
Cut the edge about once monthly, or as needed to redefine the border because of erosion or grass growing near the edge.