These raised beds are pretty simple to build. For each bed, you need three 2x8x10 pieces of lumber. I like to use untreated whitewood, because I don't want to worry about chemicals that leech out of the pressure treated pine. I usually get the people at the big box store to cut one of the pieces in half for me, since I don't yet own an electric saw. I then make a rectangle and secure each joint with two 3" weather resistant deck screws. I want to weatherseal the wood, so I am going to apply a couple coats of boiled linseed oil this weekend. Again, I'm using linseed oil so that I can avoid chemicals from a traditional wood stain leeching into the garden. Each bed costs about $20 to build.
Filling the beds up is what takes a fair bit of time and money. To prevent the grass from growing up into the new beds, I layer flattened cardboard boxes at the bottom of each. This makes it pretty much impossible for the grass to grow up into the bed, and will naturally decompose and serve as a carbon source for the soil. After that, I take the "lasagna gardening" approach. Each time I mow the lawn, I save the clippings and use them to make about a 4" layer of grass above the cardboard. Next, I layer about 3.8 cu ft of sphagnum peat moss. On top of that goes 120 lbs of top soil followed by 1.5 cu ft of leaf compost. Finally, I pile another layer of peat moss and top everything off with another 120 lbs of top soil. The cost for all that is probably around $40 per bed.
As you can see in the first bed, this material gets me to within about 2" of the lip of the garden frame. As the materials break down, the height of the "lasagna" with shrink, but then I will just keep topping it off with more layers of grass clippings, shredded paper, or kitchen scraps. After about a year, the soil components will be all mixed together and extremely rich.
I hope to get them all filled within the next week or so. For now, the second bed (one of the originals) is the only one with anything actively growing. There are a half a dozen heads of cabbage planted here (for my Mom) and the rest is a mix of bunching onions and scallions (plus some random yellow onions that sprouted in the fridge).
|Savoy cabbage "Alcosa" after a rain shower.|
|"Guardsman" bunching onions (left) and "Golden Sweet" bulbing onions (right)|