Mother Nature applies mulch every time leaves, twigs, fruits, or other organic matter drop from trees, shrubs, and other plants. These materials decompose, enriching the soil below. Landscaping mulch does much the same thing, only in a more organized, deliberate fashion.
Visual continuity. Unify the look of your yard by using the same type and color of mulch throughout your landscape.
Soil insulation. Keep the soil in your planting beds warmer in the winter and cooler in the summer.
Weed control. Keep weed seeds, which need sun and room to grow, crowded and in the dark.
Moisture retention. Slow evaporation of water from the ground.
Soil-splash reduction and erosion control. Keep soil where in place so it doesn't wash away or splash upward and drop soil-borne diseases on plants.
Tree-trunk protection. Protect trunks from damage caused by lawn equipment getting too near with mulch placed around the trunks of trees to the drip line.
Soil-compaction prevention and soil crusting. Prevent soil compaction and/or crusting so water can filter through easily.
There are many kinds of landscaping mulch, each with benefits and drawbacks. The biggest differences are between organic and inorganic mulches.
Organic mulches break down over time, adding nutrients to the soil. They must be replenished periodically. Organic mulches include shredded or chipped hardwood or bark, sawdust, straw, shredded leaves, newspaper, aged manure, compost, grass clippings, and pine needles. Cocoa, cottonseed, or pecan hulls, where available, also are considered organic mulches.
Inorganic mulches do not decompose, though organic material, such as leaves and humus, can accumulate on top of them. Inorganic mulches include gravel or other stones, plastic, landscape fabric, and shredded rubber.
When making your choice about which landscaping mulch to use, consider these pros and cons:
Shredded or chipped hardwood or bark
Benefits: Effective; attractive; organic.
Drawbacks: Large wood chips may wash away; as the wood decomposes, it pulls nitrogen from the soil. Avoid bargain mulches, which may contain weed seeds.
Benefits: Acidifies the soil for rhododendrons and blueberries; organic.
Drawbacks: Weeds sprout easily. Nitrogen fertilizer may be needed to replace the nitrogen pulled out of the soil to decompose the sawdust. A crusty top forms so it is harder for water to penetrate. Check the sawdust source carefully because it shouldn't be from treated wood.
Benefits: Inexpensive; suppresses weeds; good for winter vegetable garden insulation; organic.
Drawbacks: Unattractive; decomposes rapidly; flammable; may contain weed seeds.
Benefits: Free from your own yard; organic.
Drawbacks: Decomposes rapidly; large-leaf species (oaks, maples, sycamores, etc.) need to be shredded first so they don't form a mat.
Benefits: Inexpensive way to recycle newspapers (use three layers); suppresses weeds; organic.
Drawbacks: Must use another mulch to weigh newsprint down; cannot use slick inserts.
Benefits: Excellent source of soil nutrients; organic.
Drawbacks: Must be aged at least six months to avoid "burning" plants. Depending on the source, it may have an odor when wet and may harbor weed seeds.
Benefits: Excellent soil amendment; organic.
Drawbacks: May contain weed seeds.
Benefits: Free from your lawn; organic if you don't use lawn chemicals.
Drawbacks: Best used on the lawn. Use only weed-free, chemically untreated, dry clippings (clippings must be dry because wet grass can form an impenetrable crust).
Benefits: Inexpensive if you have pines on your property; organic.
Drawbacks: Best for acid-loving trees and shrubs.
Gravel, Crushed Rock, Pebbles, Volcanic Rock
Benefits: Available in wide array of sizes and colors; won't blow away or decompose.
Drawbacks: Draws heat; difficult to keep clean; difficult to remove. Avoid alkaline limestone rocks near rhododendrons and other acid-loving plants. Must use landscape fabric below rocks so they don't migrate into the soil. Loose stones may get thrown by lawnmowers; inorganic.
Benefits: Effective weed control. Plastic absorbs heat, which raises soil temperature so may be useful in vegetable gardens where warm soil is desired.
Drawbacks: May tear; unattractive. Plastic must be tacked down or held with another mulch. Soil cannot "breathe." Clear plastic allows weed growth. May retain too much moisture; inorganic.
Landscape Fabric (Geotextiles)
Benefits: Allows water and air penetration; effective in weed control.
Drawbacks: Unattractive; must be tacked down or held with another mulch. Weeds may grow through fabric cuts and cracks; inorganic.
Benefits: Available in a variety of colors; doesn't decompose or blow away.
Drawbacks: May be difficult to remove; flammable; inorganic.