This term applies to a wide array of materials that may be applied to the surface of the soil in beds and borders. They all serve basically the same roles in our gardens and may originate from either organic or inorganic sources.

A. The Role of Mulch - A nice layer of 2 or 3 inches of mulching material can do wonders for your beds and borders. The major impacts of mulch in the landscape include:

1. Moisture Conservation - A layer of mulch will cover the ground and intercept the rays of the sun. This will decrease the amount of evaporation from the soil resulting in water conservation and the need for fewer applications of irrigation. Also, organic mulches will soak up some of the water which will also discourage loss through evaporation.
    

2. Aesthetics - Decorative mulches will add to the aesthetic impact of a landscape. Using the same mulch throughout the landscape, will serve to "tie it together". This will make the total landscape appear as a cohesive unit rather than a random collection of beds and borders.
    

3. Weed Control - Weeds, especially annuals that come up from seed, will be deterred from emerging through this extra layer on top of the soil. Perennial plant weeds may still make it through but they will need to use more energy to make it to the surface. As a result of this struggle they may not be so numerous or vigorous as they would be on bare soil.
    

4. Cool the Soil - By shading the soil, the mulch will lower the soil temperature of the root zone of the plants below. This is a general benefit for most plants. For some, like clematis, who like to have "their heads (stems and flowers) in the sun but their feet (roots) in the shade" a layer of mulch may lead to a healthier, more vigorous plant.

B. Types of Landscape Mulch

1. Organic Mulch - Probably the most common type of mulching material falls into the organic category. These mulches are made up of parts of dead plants. This would include shredded bark, wood chips, recycled wood pallets, cocoa bean hulls and many other such products. Some of these are artificially dyed in order to maintain their color throughout the summer.
   

2. Inorganic Mulch - Stones, rocks and pebbles of various sizes, shapes and colors would fall into this category. These materials may absorb heat and actually raise the temperature of the soil below. Be careful to be sure that a stone mulch fits in with the design intent for your landscape.
    

3. Synthetic Mulch - There are several synthetic fabrics that are routinely used in landscape beds and borders. In the olden days, it was common to use a layer of black plastic as mulch. The plastic was usually covered with another layer of rocks or organic material. These installations looked good the day the job was done but the plastic would eventually become brittle and begin to shred apart. It would often give the area a very messy appearance. Although it does block the growth of most weeds, plastic does not allow moisture to penetrate to the roots of the desired plants.

   Today, there are several woven fabric materials that allow moisture and oxygen to penetrate while blocking the growth of weeds from below. The down side is that soil will often accumulate on top of the fabric over the years. Eventually, weeds may be able to take root and grow.