Mulch is a covering used over soil in vegetable gardens, flower gardens and around trees and shrubs. Benefits of mulch include soil moisture conservation, temperature moderation, erosion control and weed reduction. Organic mulches break down over time and add organic matter to the soil. Inorganic mulches are longer lasting and do not add to the soil structure or nutrition. Inorganic mulches may be difficult to remove because they cannot be incorporated into the soil.
Bark and Wood Chips
Bark and wood chips last one or two years, depending on the size and type of wood. A 3- to 4-inch layer should be sufficient. Avoid placing bark and wood chip mulches close to house foundations because it can attract termites.
Pine needles are useful, and free if you have a lot of pine trees in the landscape. Pine needles are acidic and especially good for azaleas, rhododendrons, blueberries and other acid-loving plants. Apply a 3- to 4-inch layer and be aware that pine needles may mat down, interfering with air and water movement. Replace pine needles every one to two years.
Straw tends to look messy, but may be useful in vegetable gardens. Straw may contain weed seeds and harbor disease. Straw does not last as long as other organic material and must be replaced frequently.
Pebbles or Gravel
Pebbles or gravel, inorganic mulch material, are available in various sizes and colors. Avoid lighter colored stones because they reflect heat near plants and may raise the house temperatures in summer if placed around the foundation, according to University of Rhode Island Extension.
Lawn clippings are good for gardens--they decompose slowly and improve soil, but be wary of weed seeds or grass that may contain herbicides.
Leaves are readily available, and should be shredded before use, but may blow away easily. Leaves may also become matted and impede water and air movement if applied more than 3 or 4 inches thick.
Landscape fabric is constructed to allow air and water movement and lasts indefinitely. It usually requires a light covering of another mulch material. Depending on the top mulch used on the fabric, weed seeds may easily germinate on the surface.