The size of your raised bed garden is something that you can choose, but staying within certain guidelines will make things easier. Stick with a four-foot maximum on width so you can reach all the plants without straining. Theoretically, you could make it as long as you want (or as long as space permits). Many gardeners choose to create raised beds that are four feet on each side. You can scatter around several your landscape, or make one long bed.
Standard lumber is an acceptable choice for materials. The height of the edges depends on your vegetable choices. Shallow-root veggies like lettuce, spinach and radishes will do fine in a two-by-six frame. Larger vegetables like tomatoes and corn will thrive in deeper raised beds. If you use two-by-twelve boards, you can create a soil depth of about ten inches.
When you buy the lumber, you’ll have to decide between treated and untreated lumber. If your frame is untreated, you had better plan on replacing it in a few years after it rots. However, treated wood could potentially leech toxic chemicals into your garden soil. The chemicals will likely be picked up by your vegetables and passed on to you and your family.
Safety would dictate choosing untreated wood. On the other hand, most experts claim that the small amount of chemicals you are likely to ingest presents no danger to your health. Ultimately it is a personal choice. Whatever decision you are comfortable with should be fine.
Get your lumber cut at the store before you take it home. This will help the ends fit together and keep your soil from leaking out. This is hard to accomplish at home unless you have a big saw and some skills using it. Anything handheld, like a handsaw or circular saw, probably isn’t enough.
Attaching the frame pieces to each other works best with four-inch ribbed deck nails. These raised bed gardening frames need to be able to hold in a lot of pressure with soil and plant material. Regular nails may not have what it takes to keep it together.
A flat surface for assembly will make your frame sturdier. Your driveway or deck (assuming they are flat) would be ideal. The only downside is moving the frame to your garden spot. You might need to line up some helpers. (Bribe them with future vegetables!)
If you choose to have multiple boxes, put them two or three feet apart. Give yourself enough room to move between them effortlessly. Get them in the right spot from the beginning. Once you put the soil inside, they will be pretty much impossible to move without taking out the dirt.
What about the soil under the raised bed? Till it if you like, but it’s not required. If your plants need more than six to twelve inches of soil, they’ll be able to push into the untilled dirt under the bed. Just make sure you put in high quality soil to help your plants thrive.
Commercial potting soil is okay, but try to improve its quality even more. Adding organic material should do the trick. Composted manure, homemade compost, or other organic materials will boost the quality of your soil quickly.