Mulch Materials (5014)

Mulches offer your garden and landscape many benefits. They cover the soil surface around plants and help hold moisture in the soil. Mulches also moderate soil temperature, reduce soil erosion and compaction, and keep lawn mowers and weed whips away from tree trunks. Mulches also prevent mud and some disease organisms from splashing up onto leaves, flowers, and fruits.

The two types of mulch, organic and inorganic, each have advantages and disadvantages. Organic mulches originate from plant and animal wastes. Organic mulches include shredded bark, chipped bark and wood, rotted animal manure, compost, leaves, pine needles, grass clippings, sawdust, cocoa bean shells, and rice hulls. Inorganic mulches include a wide variety of stone products, black and clear plastic sheeting, and black synthetic fabrics, often called weed barriers. You typically use weed barriers beneath stone or bark mulch, although you can use them alone as mulch in vegetable gardens. These materials raise the soil temperature for warm-season crops like tomatoes and peppers.

Organic mulches like grass clippings, newspaper, bark chips, etc., slowly decay over time. While decaying, they add organic material and nutrients to the soil. Organic matter improves drainage in clay soils and water-holding capacity in sandy soils.

Inorganic mulches do not decay and so do not add anything to the soil. Replenish organic materials each year or two as needed. Stone mulches placed on weed barriers are permanent and do not need top-dressing.

When you apply a two- to three-inch layer of organic mulch, you do not need a plastic or fabric weed barrier mat beneath the mulches to control weeds. To provide adequate weed control, stone mulches need a weed barrier. Unfortunately, mulches applied over weed barriers often shift over time, especially on slopes. In addition, organic matter that builds up over weed barriers creates the perfect growing conditions for weeds. Organic mulches are usually less expensive than inorganic mulches. You can often get inexpensive or free loads of wood chips from tree services, city and county parks departments, and local utilities. You can also use yard waste materials, such as grass clippings and leaves, as mulch around landscape plants and in the garden. You can also use compost as mulch.

Although stone mulches are more expensive, you do not have to replenish them if properly used. Place stone mulch over synthetic weed barriers. This prevents stones from mixing with the soil below. Stones come in many colors and sizes. Avoid using white stone mulches, especially limestone and marble chips, because they can adversely affect soil pH. White stone mulch also reflects heat and detracts from the rest of the landscape.

Remember, leaves, twigs, and other organic matter may collect in stone mulch. You will need to clean out the material or live with that appearance.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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