The following post comes from the Utah State Extension Office:
Although it is more work, finished, neat edges can make a landscape look polished and attractive. A lawn area may look green and lush, but if the edges are uneven or untrimmed, the whole yard can seem unkempt. Consider these tips to keep your landscape tidy.
• Remove and prevent grass from growing where it cannot be easily reached by a mower. This will help reduce edging time. Spray a non-selective herbicide such as Roundup or Finale to kill the grass and weeds around trees, fence posts, walls and rocks. Leave a large grass-free zone around trees and a smaller strip around rocks, fences and walls.
• Mix a pre-emergent herbicide such as Surflan with Roundup to prevent grass and weeds from returning. This kills existing weeds and deters germination for a few weeks.
• Design the landscaped area so it requires a minimal amount of edging or trimming. This means trees, shrubs and flowers should not be placed in the lawn, but in separate planting areas. Surround fences and rocks with some sort of edging material to prevent weeds and grass from growing up the fence or around the rocks.
• Consider the various materials that can be used as an edge around flower and shrub beds. Cement, redwood binder board, vinyl, rubber, bricks and other materials all reduce the amount of trimming required. There is no perfect edging material, however. Each has its benefits and drawbacks.
• Black, thick rubber edging material holds its shape for many years, but can be expensive. Cheaper vinyl and plastic products are inexpensive, but tend to lose their shape over time. Redwood eventually wears out, but is attractive and natural looking for many years. Cement, bricks and other hard materials last for many years, but can also be costly. Cement edging appears cold in a landscape and makes it difficult to change the shape of beds. Bricks are usually very moveable, but can be too mobile at times.
• One cost-free option for maintaining a clean appearance and keeping the grass in its place is to cut along the edge with a spade or shovel, leaving a 6-inch deep cut between the bed and the grass. A small scoop shovel leaves a straighter edge. This method needs to be repeated two or three times a year.