Mulches for Home Grounds: Selection

What should you consider when choosing mulch for your home grounds?

The selection of a mulch depends on its intended use. Consider the size of the area in relation to the cost of materials and availability (Table 1). Table 2 lists advantages and disadvantages of organic and inorganic mulches.

If appearance is the main goal, inorganic or inert mulches may be the best choice. If the main objective is soil improvement, consider an organic mulch that gradually breaks down. If the area is used primarily for annual flowers, it often is more practical to use a temporary organic mulch, such as composted leaves or grass clippings, that can be turned under each fall.

Mulches can be used to prevent soil erosion by wind and rain. In windy areas, gravel or rock mulch may be preferred over lightweight organic mulches. Any mulch that reduces the impact of raindrops will help reduce water erosion, just make sure the soil surface is entirely covered with mulch.

Black plastic (polyethylene) is not recommended as a mulch in landscape areas. Black plastic is impermeable therefore no oxygen exchange can occur in the soil. Lack of oxygen to the roots significantly reduces plant growth. Black plastic also prevents water penetration. If a weed barrier is needed, use landscape fabrics instead to allow water and oxygen exchange.

Table 1: Area covered to a given depth by one cubic yard of mulch.
Area (sq. feet)	Depth of mulch (inches)
80	4
100	3
160	2
325	1

Table 2: Types of mulches and their advantages and disadvantages.
Mulch type	Advantages	Disadvantages	General Comments
Organic Mulches
Cocoa-bean hulls	Long lasting, dark brown color.	Compact; forms a crusty surface. Expensive.	Molds may form on surface. Harmless if stirred to break crust.
Crushed corncobs	Uniform in color.	May retain too much moisture at surface or compact if kept wet.	Cobs dyed various colors. Availability limited in some areas.
Grass clippings	Readily available. Nutrient recycling.	Must be applied loosely, in thin layers to reduce matting. Herbicide residues may harm plants.	Allow grass to dry to prevent matting before applying as a mulch.
Hops	Attractive color. Nonflammable.	Disagreeable odor until dry. May blow away.	May be available from local brewery.
Leaves (composted)	Readily available. Nutrient recycling.	Not very attractive. May become matted.	Good soil amendment.
Leaves (fresh dried)	Readily available. Nutrient recycling.	Not very attractive. May blow away. Fire hazard. Wet leaves compact into slimy mats.	Most appropriate in naturalized Gardens or shrub masses.
Manure (strawy)	Usually available. Adds nitrogen and other nutrients to the soil.	Unpleasant odor. Weed seeds. Not very attractive.	Better soil amendment than mulch. Should be aged and/or heat treated.
Newspaper	Readily available. Good for preventing soil splashing (disease) on lower leaves or vegetables.	Don't use color inserts or red ink. Not very attractive unless covered.	Use 3 to 6 sheets thick and cover with organic mulches.
Peat (sphagnum)	Usually available in bulk amounts. Can be incorported into the soil to improve aeration.	May crust on surface. May blow away.	The only acid-forming peat, but even this is variable with source. Best used as a soil amendment, not as a mulch.
Pine needles	Attractive. Do not compact.	Difficult to obtain in quantity. Can be a fire hazard.	Best for winter protection of fall-transplanted material.
Shredded bark, bark chips, chunk bark	Long-lasting, attractive. Does not blow away easily.	Cost relatively high. Shredded bark may compact. Large bark chunks may impede spreading perennials.	Use for informal walkways.
Straw	Readily available.	Blows easily. Highly flammable. Weed seeds often present.	Best used as a temporary mulch around plants needing protection in winter. Anchor with wire mesh.
Wood chips, shavings, pole peelings, recycled shingles	Long lasting. Readily available. Does not blow away. Popular in perennial gardens.	Texture and color not uniform. Can cause nitrogen deficiencies in plants if incorporated into the soil.	Rustic but usually attractive. Will not compact readily.
Inorganic, inert mulches
Clay aggregates (heat treated)	Gray/brown colors available. Lighter than gravel, easier to transport. Weed-free.	Expensive.	Brand names available (Turface, Terragreen).
Weed-barrier fabrics	Reduces weeds. Allows air and water penetration. Long lasting if covered with mulch. Easy to apply.	Some may be costly. Most deteriorate in sunlight unless covered with another mulch material such as wood chips.	A good substitute for black plastics.
Recycled rubber tires	Long lasting. Uniform color. Does not blow away.	Heat can build up around homes with this type of mulch. Not biodegradeable.	Newer product; supply more limited.
Gravel, stone, pea gravel, pebbles	Available in colors to match or complement the architecture. Inexpensive.	Will not prevent growth of some weedy grasses. Heat can build up around homes with this type of mulch.	Use weed fabric beneath to prevent weeds.

Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. CSU Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.

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