Please allow me to express my sympathies with those of you who have difficulties with weeds in your gardens. I have no doubt that the weeds which have been mentioned – goose grass, chickweed, bindweed – all present real difficulties for gardeners. I do not recognise any of these weeds, (by the names which have been mentioned on this thread), but here in Australia there are many different kinds of weeds which create difficulties of various kinds.
There are several ways of combating this problem, some better than others. I believe that perhaps the most effective way, and the easiest - is through the use of mulch. I want to make a distinction here, between mulch and compost. The kind of mulch which has given me the best success had been leaf mulch, made from the leaves of deciduous trees, collected in Autumn. Many of you may have opportunity to collect large quantities of autumn leaves. I have used a mulching machine to pulverize autumn leaves so that the resulting mulch could be spread thickly around my garden. For those who do not have a mulching machine, I have found that these types of leaves can be decomposed by packing them into large plastic garbage bags, and sealing them up while the leaves are moist but not too wet. In my climate this decomposition can take several months.
The use of leaf mulch provides several benefits (although there may be other benefits as well):
- mulch made from deciduous leaves do not contain weed seeds,
- it provides a blanket layer which helps to prevent germination of weed seeds which are near the surface of the soil,
- it provides an insulating layer to protect the surface of the soil from frosts,
- it protects the soil from excessive loss of water from evaporation during hot weather,
- it provides a slow-release fertilizer of minerals such as potash, which the trees originally extracted from deeper in the soil,
- over time it helps improve the texture of the soil,
- if weeds do grow through a thick layer of mulch, they are usually much easier to pull out by the roots, because they have germinated very close to the soil surface, and the roots are most likely to be in the mulch layer,
- leaf mulch discourages snails (at least it has done so for me!)
I have found that using grass clippings as mulch can have disadvantages, in that they may contain seeds which could germinate and cause problems amongst the desirable plants. Weed seeds which germinate are usually those which are near to the surface of the soil. Weed seeds which are brought to the surface by digging the soil can germinate, even after several years of being buried, so it is desirable to keep them buried deeply for long enough to ensure that they are decomposed. To this end, I have found it very effective to dig a deep hole – maybe 12-18 inches deep, and wide enough to bury the quantity of weeds to be get rid of. I have used holes about 3 feet by 5 feet to be able to bury a large quantity of weeds which can then be covered by a thick layer of topsoil. In time, these weeds provide nutrient to the crops you do want to grow, and the weed seeds will never germinate if you do not bring them back to the surface.
I would not use weed matting, old carpet, or plastic sheeting to try to prevent weeds from growing. These may provide a short term benefit, but I have seen too many examples where they have failed after a year or two – and then they present a new problem because they have contaminated the soil because they are non compostable. If a weed mat of some kind is really necessary, then perhaps layers of newspaper could be used, which will in time decompose and contribute to the friability of the soil.