We recommend cutting bed edges at a 4" depth with a spade or a half moon edger.
Softly flowing lines are aesthetically pleasing, this gives a more natural look. Keep the edging line gentle and smooth. Corrective edging may be required to correct imperfections or irregularities. Guard against excessive turf removal unless you plan to make a major change in the shape of the bed. This could throw off the layout of your garden.
Straight edges should be set off permanent objects - either parallel or perpendicular. Set a string line for best results.
Remove all edging scraps from bed surfaces - especially turf and weeds. If the soil is clumped it should be broken up and raked smooth prior to mulching.
Step back and look at the edging from a distance to be sure you have created a line that is pleasing to the eye.