If you have ever planted anything then you know that soil preparation matters! Most gardeners go for the rototiller, its quick, and brutally efficient. However, it may not be the best tool for the job. Rototillers do a great job loosening soil and killing weeds, however, they only go 6-8 inches deep. Plant roots go much deeper. Double digging, on the other hand, loosens soil 2 feet down! Giving those roots lots more room to dig in.
Thinking like a plant
To see why the depth to which we loosen soil matters lets put ourselves in the shoes of a typical garden plant. When you first germinate and start spreading your roots you have lots of room to grow and spread. You probably have siblings nearby but you barely even notice them!
As you grow bigger and stronger you push your roots down deeper and further out. Within a few weeks, you have sent your roots down through the soft soil and reached a much harder layer of soil! You have two choices, push through the soil, or spread out horizontally. Naturally, you decide to go horizontal for now and spare yourself the effort of pushing into harder soil.
Not long after that you realize there is a problem, your siblings all made the same choice. Your roots and theirs are now weaving around each getting tangled and competing for nutrients. A little frustrated by your siblings laziness you decide you’ll have to push into the harder soil to find nutrients.
The soil is tough making progress hard! Every day it gets hotter and before long you realize that the life giving soil around you is starting to dry out! You can feel there is more moisture just a little deeper down but you as you dig with your roots that water retreats further and further away! If only the soil was just a little softer 9 inches down!
A little less dramatic
Now that we have gotten that dramatic tale of struggle out of the way let’s talk turkey. Rototillers only loosen the top layer of soil. This is great for young plants and some shallow-rooted plants. However, most plants put their roots several feet into the ground. Even onions can have roots 3 feet underground!
Now I can not really say I want anyone to loosen soil as deeply as their plants can put down roots. However, why limit ourselves to only the top 8 inches! Plants need all the help they can get! When double digging beds the soil is loosened up to 2 feet down. That’s three times as deep! Additionally, if you have really clay heavy soil, rototillers can compact the soil below the layer they loosen.
Double digging lets us help our plants by loosening, and even amending, our soil more deeply than other methods.
How to double dig
Double digging is a simple process really and only takes a few tools: a shovel, a wheelbarrow, and a broadfork or garden fork.
- Dig a trench across one end of your bed, placing the soil in the wheelbarrow.
2. Add any soil amendments you want to.
3. Work your way across your trench with your broadfork.
4. Start digging another trench right next to the first one except this time use the soil from the second trench to fill the first one.
5. Repeat steps 2-4 working your way across the bed.
6. Dump the soil from the wheelbarrow into the last trench.
Congratulations! You now have a beautiful double dug garden be that’s ready for your plants!