There are many reasons for spreading a layer of pebbles or wood chippings on top of the soil around the garden plants, otherwise known as mulching. A mulch layer is said to retard weeds, regulate the top-soil temperature, save water by reducing evaporation from the soil and prevent soil erosion. All this is true in principle, but merely spreading some mulch does not necessarily produce satisfactory results. How then can it be used most effectively?

The use of an inorganic material like decorative pebbles, is often part of an overall design, especially in Mediterranean style gardens. They are best employed as a ground cover, with a few sculptural plants dotted within them. If the bed however is to be covered by plants, then pebbles from my experience, end up being more of a nuisance than a benefit, because they make plant feeding and weed removal amongst other tasks, more problematical.

Let's take then a situation where a prostrate ground cover species is to be planted at a distance of one meter between the plants. The two principle advantages of spreading an organic mulch such as wood chippings between the plants, is that the soil conditions are actually improved, and the temperature of the top layers of the soil are regulated. This is of considerable significance in hot dry climates, where the temperature at the soils' surface can reach 50c and more.

Mulching cannot be isolated from other gardening tasks such as feeding. An excellent way of overcoming the practical inconvenience of feeding the plants through an existing mulch layer, is to incorporate into the soil, massive quantities of compost before planting. If compost is dug in to the soil at a rate of 60 liters per square meter, then together with the wood chippings slowly adding humus to the soil as they break down, there should be little reason to feed for about 5 years! Added to the fact that with a mulch layer, there is no need to hoe and cultivate the top soil, a significant saving in labor can be achieved. One word of warning though. With such quantities only use compost that has been thoroughly broken down and is from a known and reliable source.

Despite its many benefits, it is important to recognize the limitations of mulching. To be effective in retarding weeds, organic mulches should be spread to a net depth of at least 10cm. As at least 5cm is liable to settle, the gross depth of material should therefore be some 15cm. This makes wood chippings a relatively expensive option. Mulches, while significantly reducing the germination rate amongst annual weed seeds, generally have little effect on perennial weeds. With regard to saving water, they are most suitable for drip irrigation, but much less so where sprinklers are used, as the mulch layer absorbs a considerable amount of the moisture dispersed by the sprinklers.

For further information on this topic, click on the link below, and then on the Articles page where the following, arranged alphabetically can be found:

* Preventing Weeds In A Winter Mediterranean Garden

*Five Excellent Reasons For Mulching Your Garden Beds