Raised beds can make gardening feasible where it otherwise wouldn’t be, like when all you have available is concrete slab or a driveway. They also just make gardening more feasible, period. Rather than plant in the native soil (or go through the work of amending it) you can plant in what is essentially a box of premium soil, and a more easily controlled environment. Working a raised bed is also a lot more comfortable than working one at ground level.
Choosing the best location
The best part about using raised beds is that you can literally put them anywhere. Even if all the available space you have is a paved driveway, you can build a raised bed garden right over it. Like with any garden, your raised beds need to be somewhere they can get the right amount of sunlight. Your own convenience is another important factor. The closer your gardens are to the house, the less time you’ll spend going back and forth --- and the more likely you’ll be to tend your beds at all on days when you’re rushed or tired.
Choosing the right size
Once you have the location established, you know how large of an area you can take up for your gardens. There’s no limit to how long you can make your beds, but its recommended to keep them at 48” or less in width, so that every square inch can be easily reached from at least one side of the bed.
12” is the recommended minimum height. The worse the native ground underneath is, the taller you’ll want your bed to be, so it offers a good base of healthy soil. If you’re building over concrete, keep in mind that your roots won’t be able to penetrate if they ever reach the bottom. 16-18” happens to be a pretty comfortable height to work over and to sit on, though you may find a slightly taller height even better.
Going much taller shouldn’t be a problem. You could go to 36” or even taller if you wanted. That will require a lot of soil, and a lot more material for building the frame. Also, the taller you go, the more the weight of the soil exudes pressure on the frame, so taller beds will need to be more strongly reinforced. The expenses, time, and effort add up, so you need a strong reason to build taller beds.
Choosing your materials
The variety of different materials available is nearly endless. All you really need is something cost effective, easy to handle/work, and safe for human, plant and animal contact. Kits for raised beds are available on the internet, and some have a decent value. If you’re not concerned with price, or don’t have time to search around, or you’re just not building many boxes, kits might be a good route for you.
Other options are sheet material (like corrugated metal), masonry (like cinder blocks), or lumber. Make sure you have a means to cut the material you choose as needed. Raw lumber can be used, but will eventually rot and need to be replaced. Some varieties will last longer than others, but as a general rule these are more expensive and harder to come by. Treated lumber, on the other hand, might never need to be replaced. This is the easier and cheaper choice, but there is a small element of risk involved: treatment processes usually involve hazardous chemicals like copper, which can be drawn up by plants, poisoning the plants. However, healthy soil with a neutral pH will prevent the uptake of copper. Additionally, high copper levels would theoretically kill plants before you ever ate them. There is a small risk, but people have been using treated materials, such as salvaged railroad ties, for a long time. Just keep your soil healthy and keep an eye on your pH.
On assembling your raised bed(s)
There’s no right and wrong way to put the frames together. They’re a fairly simple job that anybody can do with a little effort. All that really matters is that they hold the soil in place and continue to do so under potentially adverse conditions like wind and heavy rain. Lumber frames can be held together with fasteners like screws or nails if you prefer. An alternative that works for sheet materials, as well as boards, is to drive vertical stakes into the ground that hold the boards/sheets together. Stakes can be made out of boards like 2x2’s or 2x4’s, by cutting the end into a sharp point.
Of course, composting is the best way to keep up the soil in your beds. If your garden’s demand for compost isn’t met by your how much your household produces, you can visit the Waeco yard next to the Fairgrounds in Monroe for high quality organic compost, in addition to other landscaping products like bark mulch and topsoil.