Raised beds have many advantages: they prevent soil compaction, alleviate some weed pressure, and require less bending over. Their soil also warms more quickly in the spring, which allows for earlier planting. But, most importantly, they provide excellent drainage. When drainage is poor, raised beds are the way to go. Raised beds can be built by simply mounding native soil mixed with compost (60/40 soil/compost or up to 50/50). If you are creating rows, make them 3 to 4 feet wide and dig the sides down to create paths. Of course, you can also construct walls for your raised beds with wood, brick, rock, etc.
We build our raised beds out of 2x redwood lumber. Redwood is expensive, but it lasts a long time and looks great in our foodscape. Pine or fir can also be used and is much less expensive. We build our beds 8 to 15 inches tall. Our first redwood bed used 8ft long 2x8s and was a more elaborate U-shaped design with two levels. Our recent installation uses 10ft long 2x12s to make a simpler 4×10 bed with six inch benches on each side:
To see how we built the above rectangle bed, see our Foodscaping our frontyard video, starting around 1:15. For more information on raised bed construction see USU Extension’s video. To fill our raised beds, we use a technique called sheet mulching, aka lasagna gardening. When building over lawn, we start by mowing the lawn as low as possible, soaking it and covering it with a soaked layer of cardboard. Then, you basically build layers up the same way you make compost. You alternate layers of ‘green’ materials (grass clippings, kitchen fruit/vegetable scraps, coffee grounds, etc) and ‘brown’ materials (brown leaves, straw, sawdust, etc). We put the food scraps toward the bottom (to eliminate odor and avoid attracting animals), then add alternating layer of leaves and coffee grounds, and a sprinkle of Azomite organic trace minerals. We usually mix in a layer of finished compost in the middle and always top it off with finished compost. Many lasagna gardeners top with weed-free straw. If you have weed-free topsoil you can also add it in layers.
The great thing about brown leaves and coffee grounds is you can typically get both of them for free. Last fall we not only used leaves from our own trees, but we also asked some of our neighbors for their bagged leaves that they were planning to dispose of. They were more than happy to let us take them. Meanwhile, we collected spent coffee grounds from local coffee shops. Some shops have bagged coffee grounds ready for gardeners to pick up at any time and others were more than happy to fill five gallon buckets that we left with them.
Beds can be filled with the lasagna method any time of year. We build and fill our beds in the fall for the easy access to leaves and so they benefit from winter moisture and time to break down. In the spring, if you top your lasagna garden with a thicker layer (3 to 4 inches) of compost or a topsoil/compost mix, you can plant in them right away!