Mulches are either organic or inorganic material placed on the soil around vegetable plants. Mulches perform a number of useful functions. They protect against soil erosion by breaking the force of heavy rains; they help prevent soil compaction; they discourage the growth of weeds; and they reduce certain disease problems. Mulches are insulators, making it possible to keep the soil warmer during cool weather and cooler during warm weather. Organic mulches also improve the soil texture. Sometimes mulches can improve the appearance of a vegetable garden by giving it a neater, more finished look.

Your plants will need less water if you use a mulch, increasing the time that plants can go between watering. When the soil dries out, plants slow their growth -- or stop growing altogether. Swift, steady growth is important for the best-tasting fruits and vegetables. Mulches keep the soil evenly moist.

Mulches do not eliminate weeds. They can, however, help control them if the area has been cleared of weeds to begin with. If the mulch is thick enough, weeds that are already growing won't be able to push through and darkness will frustrate the germination of others. Persistent weeds can push their way through most mulch, but if they're cut off at the soil level a few times, they will die.

Whether you use an organic or an inorganic mulch, take care not to put it down before the soil has warmed up in the spring. If you put it down too soon, mulch will prevent the soil from warming and slow down root development.

Organic mulches are organic materials that, when laid on the soil, decompose to feed soil microorganisms and improve the quality of the soil. If the mulch you've put down is decomposing quickly, add nitrogen to make up for nitrogen consumed by bacteria.

The following are organic materials commonly used as mulches in vegetable gardens:

Compost: Partially decomposed compost looks a little rough, but it makes a great mulch and soil conditioner.

Lawn Clippings: Do not use clippings from a lawn that has been treated with a herbicide or weed killer; these substances can kill the vegetables you're trying to grow. Let untreated clippings dry before putting them around your garden; fresh grass mats down and smells bad while it's decomposing.

Leaf Mold: Leaves are cheap and usually easy to find, but they blow around and are hard to keep in place. They will stay in place better if they're ground up and partially decomposed. Nitrogen should be added to leaf mold. Do not use walnut leaves; they contain iodine, which is toxic to some vegetable plants.

Sawdust: Sawdust is often available for the asking, but it requires added nitrogen to prevent microorganisms from depleting the soil's nitrogen supply. If possible, allow sawdust to decompose for a year before using it as a mulch.

Straw: Straw is messy and hard to apply in small areas, but it is an excellent mulch. Be sure not to use hay, which contains many weed seeds.

Wood Chips or Shavings: Wood chips, like sawdust, decompose slowly and should be allowed to partially decompose for a year before being used as mulch. Additional nitrogen will be needed to supply bacteria during decomposition.

Inorganic mulch, or landscape fabric, is used in small gardens for plants that are grown in a group or a hill, such as cucumbers, squash, or pumpkins. It can also be used for individual plants such as peppers, tomatoes, and eggplants. Fabric should not be used for crops that need a cool growing season -- cabbage or cauliflower, for instance -- unless it's covered with a thick layer of light-reflecting material, such as sawdust.

There are several advantages to growing with a landscape fabric mulch. Fabric reduces the loss of soil moisture, raises the soil temperature, and speeds up crop maturity. Weeds are discouraged, because the fabric cuts off their light supply. This means you won't have to cultivate as much, reducing the risk of root damage. The fabric also helps keep the plants cleaner. When you're making a new garden in a formerly grassy area -- if you've dug up a lawn, for instance -- fabric can keep the grass from coming back.

There are some disadvantages to keep in mind as well. You will have to water more frequently, especially well-drained, sandy soils. On the other hand, plants can wilt and rot if the soil moisture is kept at too high a level and there isn't enough air in the soil. Remember too that the fabric is inorganic, and at the end of the season you'll have to remove it from the garden. If the fabric is of high grade, you may be able to reuse it the following season.

Learn how to apply both organic and inorganic mulches to your vegetable garden in the next section.

Want more information about vegetable gardens? Try:
  • Caring for a Vegetable Garden: Read our guide to nurturing your vegetable plants for the best harvest.
  • Vegetable Gardens: Find out everything you wanted to know about vegetable gardening.
  • Vegetables: Pick out your favorite vegetables to plant in next year's garden.
  • Gardening: We answer all of your general gardening questions in this section.
  • Garden Care: Whether you're growing cucumbers or columbines, we have all the information you need to nurture a thriving garden.