The lone voice of horticultural reason

Dastardly Double-Digging

5-22-1997 — As with trombone, no one is sure who invented double-digging or when; all I can guarantee is that it came before the advent of the rototiller. Why the technique is still commonly espoused in gardening books and magazines when one can readily buy or rent a machine to do the work of preparing gardening soil I thought I’d never know until this past weekend, when I had a small rhododendron bed to prepare and discovered my neighbor’s rototiller was on the blink.

Our deal has always been that I store his machine in my garage all winter, then he uses it one day each spring and I get to use it the rest of the year. But now it’s late Sunday afternoon, the thing will start but not run, the rental places are shutting down and I decide to heck with it, I’ll double-dig. Just in case you are ever faced with a similar situation, here goes:

You start at one end of the garden, about a foot in, your back to the remaining length of the bed, and as deep as the shovel will dig remove the soil along the entire end, moving sideways after each shovel full. Throw it on a tarp. You have now dug out an area measuring one foot by the width of the bed; the first row, so to speak. Now with the shovel you turn over and bust up the soil that was underneath the soil you just removed. Next take a step straight back and dig up the top layer of the “second row”, tossing this soil a foot to replace the soil you threw on the tarp. Then bust up the soil underneath, take a step back, etc. In other words, you’re simply shuffling the top eight inches of soil one foot over for the whole length of the bed, while turning over the soil underneath it each time it appears. At the end, you take the soil from the tarp – your first row – and use it as the top layer in the last row.

It doesn’t even look that good on paper. The soil you’re dealing with at the second layer is almost always junk, and no amount of digging and chopping and slicing is ever going to break it down so it would sift through your fingers. To add copious amounts of organic matter or, heaven help you, sharp sand and get it to mix in deeply and thoroughly using nothing more than a shovel is possible only if you take forever. Much better, and ultimately quicker, to shovel off all the topsoil then rototill the heck out of what’s underneath, adding organic matter and sand. Then shovel the topsoil back on and give it a second pass with the tiller, as described last week, unless the bed is very small and you need the workout double-digging will force upon you.

If you rent a rototiller and are creating a large bed in an area with gravel or clay, rent a big one-eight horsepower and very heavy. Large rental shops usually rent much bigger tillers than hardware stores that rent on the side. If you’re handy with tools, you can usually remove altogether the adjustable skid bar that limits depth, plus change the throttle cable length setting and dicker with the carburetor until that lumbering unit runs screaming hot with tines spinning like mad. Rather than the advertised eight-inch tilling depth, lean on it and you’re down twelve inches, easy. Wear safety glasses and don’t worry about rocks-it’ll split ’em. A big advantage over owning: nothing tills deeper than a rental rototiller.

What exactly is Ph? I’m certain I have no idea. It may possibly be related to science, forever a perfectly alien concept to me. During my science classes at Minnetonka I recall learning blues harmonica.

  • Friable loam best.
  • Slightly acid pH 6–6.5.
  • Drainage essential.
  • Worms good.
  • Improving soil in a vegetable garden may bring better results the second and following years than the first.

Don Engebretson
The Renegade Gardener