Double Digging Helps Make Great Gardens

By Jim Janke | Apr 01, 2013

For plants, the soil is EVERYTHING. Soil provides physical support, acts as a water reservoir, and is a home for beneficial organisms. Ideal soil is about one quarter air, one quarter water, and half solid materials. Compacted soils have too little air. Wet soils have poor drainage.

“Double Digging” is the best way to improve your soil. It adds organic matter, improves drainage & aeration, and makes it easy for plants to grow and thrive. Here’s how I “double dig” my planting beds before any planting begins.

Get the soil tested first, and add any recommended amendments. Before you dig, grab a handful of soil and squeeze it. If it falls apart you can start digging, but if it stays in a lump, the soil is too wet. Digging when the soil is too wet will create big clumps that will last all year. Wait a few days and try again. If you plan to plant in early spring, dig the previous fall, leaving the bed bumpy to help freeze out overwintering insects.

This procedure assumes you are creating a raised bed. For an unbordered garden area just skip the first step.

  1. Set the box for the raised bed on level ground.
  2. Dig a 12 inch wide, 12 inch deep trench across the bed. Set aside the soil you’ve removed.
  3. Take a garden fork and break up the soil in the bottom of the trench to a depth of a foot. This eliminates any hardpan “bowl” under the bed that can hold water.
  4. Add 2 to 3 inches of organic matter to the entire bed.
  5. Dig a second trench adjacent to the first trench, dumping the soil from second trench into the first trench. Break up the soil in bottom of the second trench as above. Repeat this process until you’ve dug the entire bed. Add the soil set aside from the first trench to the last trench. 
  6. Add 2 to 3 inches more organic matter to the entire bed and dig it in. For annual and vegetable beds repeat just this last step in subsequent years. The finished bed should be 6 inches or more above the surrounding soil level.

Never walk on your improved soil. Walking on the soil compacts it, making it more difficult for roots to grow (and plants to thrive.) If you absolutely must step on the bed, use a stepping board. Mine is a 1 foot by 2 foot piece of three-quarter inch plywood, with a rope attached through a hole on one end. Stepping on the board spreads out your weight more evenly, resulting in less soil compaction. The rope makes it easier to retrieve the board and hang it up in the garage.

Finished compost is an excellent source of organic matter. If you don’t have compost, try “Compost plus Cow Manure” or “Cow Manure plus Humus” at the nursery or home center. Composted steer manure will also work well, but is more expensive. Don’t use fresh manure or peat moss. Fresh manure will burn plant roots and may contain parasites. Peat moss will lower the soil pH.

Double digging is hard work, so be certain you are physically able to do this. Or hire someone who is physically fit with a strong back. But if you double dig your beds before planting you’ll have a much better garden. 

Jim Janke is an Extension Master Gardener Volunteer in Haywood County. For more information call the Haywood County Extension Center at 828-456-3575.  © 2013 NC State University. 

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