Iron Borders: This is one of the easiest borders to install. There's no digging involved, you just shove the prongs right into the ground. Use where you don't have to worry about turf creeping into a bed.
Terra Cotta Pots: These are a quirkier option. You can either turn them upside down or plant a single plant in each and line them up. Some people like to take this whimsical look even one step further and use abalone shells or recycled items. These borders will certainly add character. Use where you don't need to worry about turf creeping into a bed.
Plastic Edging: This is a nearly invisible border. It sinks almost all the way into the ground. This is more practical than it is decorative. It's usually used to separate a lawn area from a mulched planter bed and will prevent grass creep.
Garden Wall Blocks: These landscape blocks are very cost effective. They look like stone but are actually made of concrete.
Stone: You have a variety of colors and sizes to choose from. You don't necessarily have to mortar them together because some shapes stack well.
Bricks: If you're not a bricklayer you can still use these without mortaring them together. You can lay them vertically at a slant to create a formal looking border. Recycled bricks are sometimes available as well and they're much cheaper.
For edging that needs to be sunk part of the way into the soil, dig a 6-inch deep trench along the length of your outline. Remove any large rocks, roots, weeds and existing sod that are in the way. The width of the trench depends on the border. It should be the width of the stone or brick. If your border is next to a lawn, remove the existing lawn 6 inches past the edge border so you can mow around it easily. Iron borders are easily installed by simply pushing the "feet" into the soil.
Level the bottom of the trench, using sand to fill in depressions. This will ensure that the border will be sturdy and look uniform all the way down the line. Place your edging materials in the trench to create the border. Fill in the gaps with soil, making sure it's compact so the edging will stand firm.