Double digging consists of taking out a trench at the beginning of the area to be dug, about 2 ft (600 mm) wide and the depth of a spade. The soil from this trench is barrowed to the end of the piece being dug up. The earth at the base of the trench is then dug over, preferably using a fork, and broken up to the full depth of the fork. Then a further strip of ground, adjoining the original trench, is dug out in the same way, the soil from this being used to fill in the first trench, and the second spit at the base of the trench broken up as described. The whole of the area is worked in this way, the last trench being filled in with the soil originally taken out of the first trench.
The purpose of double digging is aeration and weed disposal as before, but in addition the ground is thoroughly broken up and aerated for at least 18 in. (450 mm) and drainage is considerably improved, especially in heavy soils and where large machinery has compacted the ground. But be warned, it is very hard work — although an excellent substitute for jogging. In the majority of gardens, unless the ground is particularly hard or compacted, single digging will be quite adequate for most parts, individual areas such as vegetable plots being dealt with more thoroughly at a later stage. A large piece of ground may need turning over with a rotary cultivator.
Whether or not you disregard the next stage will depend on your impatience to see a show place outside your patio doors, but the more you can bear to prepare your garden methodically and without rushing the job, generally the better the end results will be.
Ideally, you should leave your ground roughly dug for a good time to let the elements have a go at it. If you have done the job in autumn, at least the whole winter should elapse before you do anything else. If you dug the ground in spring or early summer, it is best left until autumn before further work. It is not a bad idea to leave it alone until you have got another covering of weeds. Many of these will be annual ones which have germinated from seeds you have turned up while digging, but some will have grown from the roots of perennial weeds which you buried while digging and which grew again. If you wait until they have grown up nicely but have not yet begun to seed you can deal with them in one of two ways: forking, and using weedkillers.