Mulch serves a variety of useful purposes in the garden. Mulch can retain soil moisture, control weeds, regulate soil temperature, improve soil quality and drainage, reduce mud and improve the appearance of the garden. Understanding the beneficial qualities and possible problems with each mulch will help you choose the best mulch for your garden.
Bark, Wood or Sawdust
Shredded bark or wood chips are effective mulches in many situations. When applied at a depth of less than 6 inches, shredded bark or wood chips allow moisture and air to permeate the soil while reducing the need for extensive weeding. Although mulch must be replaced periodically, shredded bark or wood chips are long-lasting mulches. Sawdust is less expensive than shredded bark or wood and is an effective mulch when applied over a layer of compost, as wet sawdust tends to form a crust. Shredded bark, wood chips and sawdust can use up high levels of soil nitrogen, which can be replaced by adding a high-nitrogen fertilizer.
Peat Moss
Although peat moss offers good weed control, peat moss used as a mulch has several drawbacks. Good weed control requires a 2- to 3-inch layer of peat moss, which is thick enough to form a hard crust that doesn't absorb moisture. Peat moss is also relatively expensive and will blow away in a strong wind. Peat moss presents environmental concerns as well, as peat moss is a nonrenewable resource harvested from bogs in fragile environments.
Compost
Compost is an effective mulch, especially when used in vegetable gardens and perennial or annual flower beds. Compost conserves moisture, deters weed growth and regulates soil temperature. Compost worked into the top few inches of the soil is especially effective as it returns nutrients to the garden as it improves drainage, especially in poor quality soil.
Leaves and Grass Clippings
Shredded leaves are an inexpensive and beneficial mulch, although finely shredded leaves may form a mat that will prevent moisture from being absorbed into the soil. Leaves return nutrients to the soil while feeding beneficial earthworms. Shredded leaves are most effective if allowed to compost slightly before using. Up to 2 inches of completely dry grass clippings makes a useful mulch. If weed killers have been used on the grass, the clippings shouldn't be used for at least three mowings.
Straw
Straw is a beneficial mulch that is easy to apply and maintain. Straw has good insulating qualities that make it useful when used to insulate tender plants during cold weather. Straw is especially effective around vegetables and fruits as its rapid decomposition provides a high level of nutrients to the soil. Because it decomposes quickly, the mulch must be replaced regularly. Good quality, weed-free straw can be expensive.
