Few edgings beat the brick and mortar edging for stability, longevity and (unfortunately) amount of work involved to finish the project. It can also be an expensive project, unless you manage to scavenge bricks left over from the building of your home or other construction project leftovers. But a little extra expense and elbow grease are often worth having a strong, stable, long-lasting edge or low retaining wall for your bed areas.
Brick and mortar edging is especially appealing when it matches the brick the home is made from, bringing the color and architecture of the home out into the landscape. It also lasts longer than wood or steel edging, and retains soil behind it better than polyboard. Because brick and mortar is a fairly permanent edging, it should only be used when the long-term landscape plan has been established.
Brick and mortar needs a footer for stability. Generally, a trench 6 to 12 inches deep is dug to accommodate the concrete for the footer. (See reference 1) If the edging is to retain soil, the footer may need to be deeper. The footer should extend four inches in front of and behind the brick edging. A reinforcing rod is often set into the center of the footer every several feet for added stability. (See reference 1)
Mortar is set on the footer and in the joints between the bricks to seal everything in place. If the edge is meant to retain more than a foot of soil or support a seat top, the bricks are often laid two deep. The mortar has to be kept moist, and should be removed from the face of the brick while it's still wet. A trowel is used to keep the top of the mortar even, as well as to scrape excess mortar from the joints. (See reference 1)
If you are laying brick and mortar edging for the first time, start with a smaller project to get the hang of it. It can be pretty disheartening to bite off more than you can chew, and wind up surrounded by hard mortar, uneven bricks and a quarter-finished retaining wall. Laying the footer, setting the brick and mortar and cleaning it up, even on a small project, takes a lot of time. Small projects give you a taste of what you're getting yourself into.
For a simpler brick edge that is not meant to retain soil, simply digging a one-inch trench as wide as the brick and setting them firmly end to end will provide a decent degree of grass barrier and mulch retention. For this method, mortar isn't necessary. While the edge might be nudged out of place from time to time, it's relatively easy to set it back in place and firm soil back around it. This method is also useful when there's a chance that bed edges might change in the near future.