Double Digging: A Hallmark of French Intensive Gardening

Double digging revitalizes garden soil and gives it better tilth

It's one of the basic practices of "French intensive" or "biointensive" organic gardening. French intensive gardening is named after 19th century market gardens in France that produced large amounts of vegetables in small spaces by enriching the soil, planting crops close together (to keep moisture in and weeds down), and topping off with season extending glass bell jars (cloches) placed over crops in cool weather.

J.I. Rodale of Pennsylvania popularized this method of gardening in the U.S. and he started the newsletter (now magazine) Organic Gardening in the 1940s. Another giant figure in modern American biointensive gardening is John Jeavons, who wrote the garden classic, How to Grow More Vegetables (the updated 8th edition). When faced with a new garden area of compacted soil, the first biointensive technique for loosening and enriching the soil is double digging.

Double Digging Technique

Tricia demonstrates in our video on double digging:

1. Mark and dig one trench, double the depth of your shovel or spade.
2. Set aside the top soil in a wheelbarrow.
3. Spread compost or soil amendment. This is an ideal time to add phosphorus deep in your soil where plant roots will be able to access it. Use soft rock phosphate or a high phosphorous fertilizer.
4. Loosen the remaining soil in the trench with a digging fork, broadfork or deep spader.
5. Repeat the process in a parallel trench, and place the topsoil from the second trench in the first trench.
6. At the end of the process the reserved top soil from the first trench is placed on the last trench.

When to Double Dig

Double dig a new garden bed any time of the year. Be sure the soil is NOT WET; digging in those conditions will damage the soil. In the photo, Tricia shows that the soil is moist but not wet. Preparing a new bed in the spring creates a home for flourishing summer vegetables, but you can also dig in late summer for cool season vegetables, or to cover crop a bed and get ready for the following summer vegetables.

Good News About Double Digging

You only have to do it once!

Here are ways to keep your soil loose in the following years:

• Don't walk on your beds.
• Add several inches of compost before winter, so the rain will water it in. This renews the microbial activity in your soil.
• The earthworms will work underground to keep your soil friable. In fact, keeping earthworms happy is an important reason for double digging. The process is partly for their benefit, to prevent the disruption of their lives. Rototilling, which is a modern alternative to double digging, can destroy earthworm tunnels (and the worms), and it can easily lead to hardpan soil that does not drain properly. Another reason behind double digging, and the preservation of the soil layers, is that different microbes live in different layers of the soil.

For more information about soil, see the fascinating book Teaming with Microbes.

Burn off those winter pounds with some double digging and pat yourself on the back for years to come!

For more information on digging tools, see our collection of broadforks for sale.