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Why Mulch?

Applying mulch to your garden is a good conservation practice. Thick mulches help prevent loss of top soil from wind and water erosion; reduce soil compaction, decrease water loss from the soil through evaporation; lessen soil temperature fluctuations and, as they decompose and become incorporated in the soil, improve soil tilth.


Mulching Materials

Weathered wood chips (nuggets or bark), sawdust, grass clippings, straw, pine needles or oak leaves, dehydrated or aged manures, chopped leaves, and compost are good mulching materials. A three-to six-inch layer will control most weed growth. Be sure not to bury any plant. Do not pile the mulch against plant bases, and always keep mulch away from plant crowns by a good three to four inches. Moist mulch laying against the plant's bark eventually results in trunk rot.

Clippings from a lawn which has not been treated with a broadleaf killer make a good mulch when mixed with another material such as peat. Clippings alone are inclined to pack down and interfere with water penetration of the soil.


Mulching for winter protection.

Winter mulching is of prime importance to transplants and of great benefit to all established plantings. Mulches for winter protection are applied after the soil has begun to harden. Too early applications provide "room and board" for small animals which move in and make their nests under the mulch in the fall. Protected by the mulch and a snow cover, they feed on bark and roots of thin-barked ornamentals and of fruit trees, in particular, during the food-scarce weeks of winter.

Winter mulches are pulled away from garden plants in early spring to promote earlier warming of the soil by the sun. New mulches for the summer are laid down after the soil has warmed and fertilizer has been applied, usually by the first or second week of June in New England. If the old winter mulch seems to be in good condition, it may be raked or pushed back in place for another year.


Types of mulch

Aluminum foil or backed paper, will not decompose, apply one layer.

Advantages: Increases light around plants; aphids and other insects avoid. Reusable.

Disadvantages: Can tear if handled roughly. Expensive. Artificial looking.

Comments: Keeps ground very cool. Apply only after ground has warmed up.

Bark chips, bio-degradable, apply 2-3 inches.

Advantages: Attractive; good for permanent mulch. Reusable.

Disadvantages: May hinder water penetration.

Comments: Decomposes slowly unless composted first. Redwood decomposes slowest; may repel insects. Reusable.

Brick chips, will not decompose, apply 2-3 inches.

Advantages: Cheaper than stone mulch. Non-flammable.

Disadvantages: Not readily available; high moisture retention. No organic matter added.

Comments: Decorative; made from brick overburns.

Compost, bio-degradable, apply 1-2 inches.

Advantages: Contributes nutrients; turns quickly to humus.

Disadvantages: Needs heating period to kill off weed seeds and diseases; may have unpleasant odor.

Comments: Plan and start ahead so compost will be ready.

Corncobs and cornstalks, bio-degradable, apply 3-4 inches.

Advantages: Readily available in most areas. Good weed control.

Disadvantages: Water doesn't penetrate well; may generate heat.

Comments: Add nitrogen to aid decomposition. Avoid diseased stalks and cobs. Best chopped.

Cottonseed hulls, bio-degradable, apply 2-4 inches.

Advantages: Fertilizing value similar cottonseed meal.

Disadvantages: Very light, wind scatters.

Comments: Keeps down weeds between rows. Top layer of another mulch prevents scattering.

Grass clippings (dry), bio-degradable, apply 2-3 inches.

Advantages: Improves soil by adding organic matter.

Disadvantages: Absorbent; may carry weed seed.

Comments: Mix with other materials to prevent packing. Bottom layer decomposes rapidly; add more.

Hay, bio-degradable, apply 4-6 inches.

Advantages: Legume hays (alfalfa) add nitrogen.

Disadvantages: First cut hay full of weed seeds. Poor weed control.

Comments: Fewer weed seeds in 2nd or 3rd cut. Fluff up during season.

Leaves, bio-degradable, apply 2-3 inches.

Advantages: Contain many trace minerals; best food for earthworms.

Disadvantages: May become soggy and pack, hindering water penetration.

Comments: Chip or mix with another mulch to prevent matting.

Paper, bio-degradable, apply 5-6 pages or 4-6 inches, shredded.

Advantages: May add trace minerals. Decomposes readily. Newspaper or scrap paper.

Disadvantages: May pack and hinder water penetration. Scatters. Lead in colored pages; use black and white only.

Comments: Hold edges with rocks or dirt. Best shredded. Frost protection.

Peanut hulls, bio-degradable, apply 2-3 inches.

Advantages: Adds nitrogen, phosphorus and potassium; decomposes rapidly.

Disadvantages: Not readily available in North.

Comments: Attractive to rodents if not completely free of peanuts.

Peat moss, bio-degradable, apply 3-5 inches.

Advantages: Clean and free of weed seeds. Improves water retention when tilled into sandy soil.

Disadvantages: Extremely absorbent, water penetration hindered; expensive. Adds little or no nutrients.

Comments: Good soil conditioner to loosen heavy soils; acidic. Decomposes slowly.

Pine needles, bio-degradable, apply 3-4 inches.

Advantages: Light; usually free of weed seeds; absorbs little moisture. Does not pack. Reusable.

Disadvantages: Decomposes very slowly.

Comments: Add nitrogen for faster decomposition. Slightly acidic.

Polyethelene (black or clear), will not decompose, apply one layer.

Advantages: Retains but absorbs no moisture. Black is effective weed control.

Disadvantages: Weeds grow under clear plastic. Rain can't go through easily. Adds no nutrients.

Comments: Warms soil--effective with tropical crops (melons, tomatoes). Ground must be moist before applying.

Rock, crushed gravel or marble chips, will not decompose, apply 1-2 inches.

Advantages: Relatively inexpensive; not absorbent. Water penetrates, non-flammable.

Disadvantages: Poor weed control. Adds no organic matter to soil.

Comments: Should be considered permanent mulch.

Salt marsh hay, bio-degradable, apply 4-6 inches.

Advantages: Usually weed-free; available in marshy areas or along coast. Long lasting.

Disadvantages: Not available to everyone. Expensive if purchased.

Comments: Till under at end of season. Chopping may make more attractive.

Straw, bio-degradable, apply 4-6 inches.

Advantages: Adds nutrients; lightens soil when tilled under at end of season.

Disadvantages: Can be a fire hazard.

Comments: Add nitrogen to aid decomposition unless aged.

Vermiculite or perlite, will not decompose, apply 1-2 inches.

Advantages: Totally sterile, so will not carry disease. No weed seeds.

Disadvantages: Expensive; very light; scatters. Hinders water penetration.

Comments: Good for greenhouse use.


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Topics: Sponsored by CIIFAD's Mulch-Based Agriculture Working Group at Cornell, this list has been set up for the interdisciplinary exchange of information on cover crops, green manures and other woody/non-woody mulch-based agricultural systems. The term "mulch" refers to a litter layer of vegetative biomass which is cut and left on (or partially incorporated into) the soil. Feel free to post questions or share information that may be relevant for others involved in research or extension of sustainable agriculture practices that include mulch as a component. Interest is primarily focused upon tropical farming systems (i.e. maize/mucuna rotation, "frijol tapado" and contour hedgerow mulch systems) that are relevant to resource-poor farmers, more general information that relates to the study of mulch-based agriculture is welcome.

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This page was last updated on November 16, 2002