Forking can be quite a satisfactory job if you have the time. You insert a sharp fork into the top spit and loosen all the weeds by the roots. These can then be removed with the fork or a rake and disposed of. Unless you have a lot of almost unremovable weeds such as bindweed (convolvulus) or couch grass, this method produces comparatively clean ground in which to replant and gives you an opportunity to dig and aerate the top layer of soil again. Organic gardeners may prefer the ‘smother’ approach, which consists of covering the weed-ridden area in black polythene for at least 12 months. This is fine if you are not in a hurry. Very persistent weeds, such as horsetail, may not respond to this treatment.
Chemicals for weed control are not entirely essential — but they can make the job of clearing the ground of weeds much simpler. In the case of those perennial weeds whose roots it is virtually impossible to remove entirely, and which will regrow if even a small piece is overlooked, it is possibly more efficient to tackle them with chemicals.
When you have a good covering of active top growth, spray all the weeds, using a herbicide. Do make sure, however, that it is suitable for your purpose. As it is likely you will wish to replant fairly soon, it is no good using a weedkiller with long-term residual effects on the soil, such as sodium chlorate, dichlobenil (Casoron G) or simazine. These herbicides remain in the soil for a considerable length of time after application and are therefore only suitable for areas required to be kept free from weeds for long periods, e.g., gravel paths or the bare ground between shrubs (not sodium chlorate for this last purpose as this is highly toxic to all plants). Also as you want to kill the roots of perennial plants, not just the top growth, there is no point in using a weedkiller such as paraquat which only kills top growth by affecting the chlorophyll and is therefore most suitable for annual weeds. The best chemical to use in such circumstances is one based on glyphosate which absorbs the poison through the green top growth and transfers it to the roots, which are subsequently killed. The chemical is neutralized when it touches the soil and after about 4 weeks (more or less, depending on the time of year and weather), the weeds will have died sufficiently for the ground to be turned over again.
At this point or, if you decide not to use a weedkiller, when the weeds have been forked out, it is a good idea to turn the ground over quickly again (single digging will be enough), incorporating at the same time some humus-forming material such as compost, well-rotted manure, etc. and possibly some form of fertilizer.