The simplest form of a raised bed is simply a mound of dirt, with sides tilted at a 45 degree angle. While this allows the soil to warm up earlier, it does not have a protective barrier to keep out weeds and heavy rainfall may erode the soil overtime, thus most gardeners opt for some type of edging to enclose in the upraised (or sunken in) soil.
What type of edging? Well it depends on your intended use, aesthetic preference, budget, and the size of your garden:
Plastic - plastic is thin, flexible, bendable, and can conform with the contours of your garden, suitable if you want a curved garden bed. Plastic is also cheap, however it's brittle, avoid stepping on it or it may snap right off.
Metal - metal is a more durable alternative to plastic at a higher cost. Opt for alumnium over steel since it won't rust. Metal can be painted if you want to avoid a reflective eyesore.
Wood - cheap and commonly available, recycled plywood is a common barrier used in garden beds. Wood will rot over time, but more decay-resistant wood such as cypress, cedar, and redwood are available at a higher cost. Remember, with wood you're stuck with a box or triangularly shaped garden bed.
Stone - stone such as bricks, cinderblocks, or more aesthetic masonry blocks are flexible, stackable, durable, and portable. However they have a high initial setup cost.
For larger unseen areas you may wish to go the more economical route by using wood or plastic, and use a more expensive option in smaller more visible locaitons.
Want to show off your raised bed gardens? Start a photo journal for your garden today or browse our fellow members' planted spaces. Questions, concerns, insights on garden beds or edging? Discuss it here in our forums!