Wednesday, October 7, 2009

Why we dig our garden beds 3 feet down!

I just came in from one of my favorite chores--overturning a double dug bed. I love it because it is so easy. Five minutes and a whole bed is done. Double digging, while a lot of work to begin with, makes future digging a breeze. And I like that.

This spring, Becca, my trusty stunt double, went out to the vegetable garden to start double digging our beds. We used to garden exclusively in double dug beds but when we moved out here and quadrupled our garden size we thought we needed to till. It seemed like too much to dig.

But after ten years watching our soil not be as delicious as we like, we decided to switch back to our old reliable form of preparing the soil--double digging and cover crops.

Here's the thing, rototilling is like running your soil through a blender. All the little friendly microbes and soil beings get turned on their heads and chewed up (so to speak). What's on top ends up on the bottom and vice versa. In the short run, rototilling is a quick solution to a big problem. But in the long run it destroys healthy soil biology which is the essence of soil fertility. And soil fertility is what determines how nutritious the food you grow is and how healthy the plants are. Healthy plants have a lot fewer pests and problems. Here's a picture of what soil looks like when it has had repeated rototilling. This guy is getting a shallow turn
instead of a deep dig like the turn of a fork would give. Most likely his soil has deep level compaction.


Ten years of rototilling has created more and more problems in my garden. Even with regular, hefty doses of biodynamic compost, leaf mulch, and all the other lovely soil building things I do, the texture of our garden soil was not improving. It dried out easily and parts of it were like a rock mid-summer--the same parts that looked gorgeous after the rototiller went by in the spring.

When I did the ultimate test of soil fryablity (throwing a fork in the ground and seeing how far the tongs descend), my garden failed abysmally. This isn't surprising, not after what I have been learning about soil health lately. But it took experiencing it first hand for me to really understand the full extent of the damage rototilling was causing to the soil.

Now don't get me wrong...our soil was fine. Way better than most, its just that I have big ideas. I want the best.

Hence my resolution to go back to double digging not matter how long it took us to dig the beds. Becca worked hard whenever she could this spring and got about a quarter of the garden dug. What a difference. Here's what the garden looked like in the beds she dug. AMAZING growth, bad picture. It looks like mayhem rather than a garden but trust me we have been eating out of this patch of garden every day for 6 months and there is no end in sight. Here's a kale plant that was as tall as I was and delicous too.
You may be wondering how to double dig a bed. I'll explain but first let me explain what the term double digging means. It refers to digging at least twice the depth of the blade of a spade, or in some cases twice the depth of the topsoil (that is if you have a LOT of topsoil). We learned to double dig from a great book by John Jeavons--How To Grow More Vegetables. He is THE urban/small plot gardening guru as far as I am concerned. I have had his book since the early 80's. Mine is in tatters from so much use, but you can still buy it new. It's a classic.

Anyway, back to the digging, after years of double digging we kind of have our own system that is reminiscent of John Jeavons but we made it our own and boy does it work. This is what we do:

You will need a spade, a fork, fresh cow manure, and some leaves or other organic matter.

1) dig off the topsoil and place it in a pile near where you are digging but out of the way.
2) keep digging through the subsoils and put that soil in a separate pile (important because you want your topsoil to end up on top)
3) dig about 3 feet down, making a straight sided pit (this is deeper than traditional double digging)
4) layer 6-8 inches of fresh (if possible, bagged if not) cow manure across the bottom of the pit I have tried other manures and in my opinion, it is worth the effort to find cow manure.
5) add 6-8 inches of organic plant matter--sometimes I use leaves, sometimes rotten hay, sometimes things from the garden, my favorite is leaves.
6) layer the subsoil back on carefully knocking any clumps apart with the fork
7) layer the topsoil back on top, carefully declumping as above
8) layer 3-4 inches of biodynamic or other organic compost on top of the bed
9) fork the compost into the topsoil
10) shape the bed into a nice rounded shape
11) plant as soon as possible with either your garden plants or a cover crop

Using this method, you will soon have a couple feet of gorgeous topsoil. Loose, fryable, and ready to grow anything.

I know it sounds like a lot of work, but if it gives you tender brocolli shoots like these every night of the week it's worth it. And then the next season, when all you have to do is lightly turn it over with a fork, then it is REALLY worth it!! If you are skeptical, just dig one bed at a time and see what you think, Bet you will be convinced. This cabbage was more than enough to convince me. Biodynamics and double digging are my garden heros.


  1. You are so inspiring...I want to go out to my garden and start digging! My hero...

  2. that cabbage is beautiful!

  3. Thank you for the information! Wonderful. :)