How to double dig
Double digging may be hard work but it’s a requirement if you are to grow giant vegetables.
What is it?
Double digging is straightforward. You just need to imagine that you have two layers. The top is dug with a spade and the bottom with a fork so you can incorporate some organic matter.
However, the moving of the soil at the beginning and end confuses gardeners who haven't double-dug before. At it's simplest, this is like the nursery rhyme: "There were ten in a bed, And the little one said Roll over, roll over. So they all rolled over and one fell out." You move the top layer of soil forward with each trench and a gap appears behind. Then, at the end, you use the soil that "fell out" at the beginning to fill the end.
When is it necessary?
In most cases, only single digging is needed, but it's a useful way of cultivating soil in new gardens and where deep top-soil is required. On poor or heavy soils and in vegetable gardens, it may be needed every three to five years, otherwise borders only need double digging at their creation and on total replanting.
When to do it?
Ideally in autumn and winter when the ground is moist but not waterlogged or frozen. The ground then has time to settle and, on heavy soils, for the frost to break down the clods before planting in spring. However, if the soil conditions are good, then it can be carried out at any time of year.
1. Use a line to mark out the area you are going to dig. Although you can buy lines, it's easy to make one with a cane pushed in at both ends of the plot and a piece of string stretched between them. Marking out the plot keeps the trench straight, making it less likely that the process will move too much soil to one end or the other.
2. Once the width is marked out, then measure approximately 60cm (2ft) back. Use a spade to dig out this area and temporarily place it to one side. As the end of digging the area, this soil is used to fill in the last trench.
3. Continue to dig the first trench, put the soil aside. The depth only needs to be the same as the spade blade.
4. Fork over the bottom of the trench. This is where the name 'double-digging' comes from, as you dig twice the depth of usual, single digging.
5. Add organic matter, such as garden compost or well-rotted manure, to the base and lightly fork in.
6. Now measure approximately up the line another 60cm (2ft), and use a cane or stake to mark where to dig to.
7. Dig out the soil and place on top of the first trench (where the organic matter was incorporated).
8. Once the soil is moved forward, you are now ready to repeat the process from step four to seven.
9. As you work up the plot, be careful to keep the top surface level. This ensures that the soil isn't shifted to one end.
10. Once you have reached the end of the plot, use a barrow to move the soil dug out at the beginning.
11. Pour it in the final trench to fill in the final top layer.
Allow the soil to settle before planting. If dug in autumn, this usually happens naturally by spring. But if the soil is still very soft, lightly tread the plot first.