Raised Bed Gardens and Double Digging

raised garden bed with perennial flowers
Raised Beds Are Great for Flower Borders

Many gardeners think of raised beds as the answer to the problem of growing vegetables in poor soil.

While raised beds can certainly make excellent vegetable beds, they need not be used exclusively for either vegetables nor in poor soil. Raised beds are a great way to grow everything.

Hands down, the absolute number one advantage of raised beds is uncompacted soil. A well planned and well-maintained raised bed will never be walked upon. The soil remains light and fluffy, allowing the roots to grow deep into the earth.

When you think about raised beds this way, you may see that the idea of building a frame and then just dumping new soil on top of old, worn out,  compacted, poor soil is really more of a recipe for a one season quick fix than a permanent new garden.

HEALTHY SOIL = HEALTHY PLANTS

Organic gardeners have a second secret they employ along with raised beds: double digging.

In a true double dig, the soil is loosened to a depth greater than 12″. The gardener first digs a trench a spade-head deep (approximately 12 inches) the entire length of the bed. The soil is removed and placed in a wheelbarrow or similar storage container. The gardener then works the trench with a digging fork, loosening and aerating the soil for another 12 inches. (Be sure to check for buried electrical cables before doing this!)

When the first trench is complete, dig a second trench right next to it. Fill in the first trench with the soil you remove from the second. Continue in this way until the entire bed has had the top 12 inches of soil turned and the second 12 inches loosened.

As you might imagine, this can be back breaking work, especially if you begin by removing sod. 

However, putting light soil on top of compact, heavy soil is not too different than putting your new garden beds directly over concrete. It is very difficult for water, fertilizer, and roots to penetrate heavy, compact soil.

Fortunately for those of us without strong backs, there is a middle ground. You need not do a full double dig to prepare your raised bed.  Even a short course of turning and improving the soil will yield improved results. Use a spade and garden fork to turn the soil and mix compost into the top three inches of the original soil. Wiggle your digging fork around to aerate and loosen the soil.

Once you’ve loosened the soil, build your frame(s) and add the new soil.

Be sure that you can reach to the center of the bed from either side. You never want to actually step into the bed or onto the soil once the garden is started. Leave garden paths between and around the beds. If your paths are grassy, be sure they are wide enough for a mower.

Photograph by psd Photo released under Creative Commons License