Raised beds serve several functions. They warm the soil by allowing the sun to warm the edges as well as the surface. They define areas for walking and planting so that planting areas don’t get compacted by walking. And they define separate areas for different crops, allowing easier and more efficient preparation of soils for specific crops.
I’m thinking about raised beds now, and am cheered by seeing the big pile of boards for my new beds in my front yard (getting covered by snow soon I hear). I thought it would be fun to take a look at different types of raised beds. I’ve seen many creative options at our community garden. I’ve seen edges made of house siding, rocks, discarded pallets.
Raised beds my husband has previously built for me are fir or pine from a local store. We used 2 x 3’s, which a a bit low, but work fine. I’m looking forward to beds made from 2 x 6’s in my new garden. We don’t use pressure treated, but you can if you prefer. It will last longer and the new pressure treating methods are not toxic like the older ones. You can also use cedar (if you can afford it). It will last longer than fir. My guess is the costs may balance out in the long run and the cedar will be less work as you need to replace less often. My fir beds are started to rot after 3 years and my husband is replaces one or two a year.
You can build beds with corner posts and then drive the corner posts into the soil and level the beds. Or you can do the reverse – drive in corner posts and then attach and leveled beds around them.
Here are some links that show bed design: