Post category: Mulches


The application of a layer of material free from weeds or weed seeds is very effective in preventing weeds. Weed seeds germinate but die because they lack adequate light. Loose mulches, such as compost, manure, bark, grass clippings, peat or gravel must be thick enough to block out light.

These only work when applied to weed-free soil, and in the case of manure and compost must be well-rotted and weed-free themselves. Organic mulches have to be topped up every couple of years, because they break down, themselves providing excellent rooting conditions for blown-in weeds.

Gravel must be kept free of fallen leaves, for the same reason. Thick black polythene is an excellent mulch, and may even be used to kill existing weeds, but it tends to split and break up after a few years. A combination of polythene and gravel is long-lasting, the gravel shielding the polythene from the sun. But weed seeds can begin to grow in the gravel.

Weed-preventing fabrics are better than polythene for this purpose because they allow water to pass through to the soil beneath. Plant debris, that would build up and provide rooting material for weeds, is more likely to rot down and pass through to the soil beneath.

Old carpet, or thick layers of newspaper or cardboard, can be used as light-excluding mulches to achieve weed control. These do not last very long but can be very effective while they last.