Raised Beds

The why and how of making raised beds:

Why? 

• Allows you to grow anywhere. 

 Soil can  range from packed clay, to a layer of sand, to the concrete patio that takes up the whole of your backyard.  If you're dealing with the typical back yard in a suburban development, you're looking at deeply suboptimal ground that will take years, even decades, of hard work and amendment to make productive.  Typically, you would be dealing with the ground that the developer bulldozed flat to create a building site.  So you turn it with a shovel, or with a rototiller and then amend it with cubic yards of peat and compost for their organics, sand to reduce compaction, and possibly lime to address the pH issues.  In the meantime, you hope that a hydraulic leak or rinsing from the concrete truck hasn't permanently poisoned your soil.

After a decade or so of constantly feeding and reconstructing the soil, you have finally overcome the limitations of your backyard and developed a fertile garden.  And it is only then that realize that you would have been better off if you hadn't had to deal with the limitations of the packed clay ground your contractor left you, and had simply used the amendments as the growing medium to start with.  Any element of that packed clay simply limited your productivity, so why use any of it at all?  The truth is that you can start immediately with a rich, productive garden, and eliminate the uncertainty.

This is especially true if you are unfortunate enough to have a concrete back yard or one that was packed gravel or a parking area where no soil at all exists.  You will be building your garden above ground and that can rest directly on a paved platform

How:
Let's start by taking a minute to asses the situation.  You need to find the location in your yard that gets the most sun throughout the day.  Avoid being too close to fences and trees that shade your garden late in the day                                                                                                                    .  You need to level the site.  If you are vulnerable to burrowing mammals, you may need to line the bottom of your raised bed with hardware cloth.

We are going to work with a raised bed that is 4 feet by 8 feet.  For our first year, we will make it out of 2x8s and it will only be one level high. You can use 2x6s for a more economical approach, or 2x10s for greater volume.  In subsequent years, we can add additional layers of 2x8s to increase the depth of the raised bed.  We will also dig down into the existing soil by 4-6" inches, giving us 10" of growing medium.  We can accomplish this simply by digging down one shovel depth and turning the sod over so the grass is on the bottom.

Next some quick math:  A raised bed of 4' x 8' by 6 inches has a volume of 16 cubic feet.  A typical bag of garden soil is measured in cubic feet, or 20 - 25 quarts.  And, there are about 25 dry quarts in a cubic foot so each bag of soil is approximately 1 cubic foot.  We need 16.  As an example the garden center has "garden soil" at $6.77 for 2 cubic feet.  We'd need 8 bags to fill the bed, for a cost of about $55.00, which is manageable if a little high. 

One recipe for filling a raised bed is:

• 4 bags (2 cubic feet each) topsoil
• 1 bale (3 cubic feet) compressed peat moss
• 2 bags (2–3 cubic feet each) compost or composted cow manure
• 2" layer of shredded leaves or grass clippings as a mulch layer on top. 

However, you may have other sources of soil around your yard including leaf mulch and compost.  A way to cut down the total volume is to begin by filling the raised bed with leaf litter, grass clippings and even small branches about 1/3 of the way and then layering your purchased garden soil on top.  After a year of being on the bottom of a working garden bed, the organic base layer will break down into compost.