ANR-0385

A L A B A M A A & M A N D A U B U R N U N I V E R S I T I E S

www.aces.edu

Mulches for the Landscape

Nature mulches plants with fallen leaves and other organic materials. Mulching, as practiced

by gardeners, is merely an adaptation of this natural process.

Advantages of MulchingMulching offers several advantages, the

greatest being conservation of soil moisture. Evaporation of water is greatly reduced when the soil is protected from the direct rays of the sun and moving air. Also, rain falling on the mulch does not pack the soil surface the way that rain falling on bare soil does. Mulch also decreases erosion.

Another important advantage of a mulch is the control of weeds. Mulch greatly reduces the need for weeding, and if used with a preemergence herbicide, which kills weeds before germination, the benefit will be even greater. It is especially important to mulch rather than cultivate around shallow-rooted plants such as rhododendrons, azaleas, and camellias.

Controlling soil temperature is another plus with mulch. Lower and more uniform soil temperatures in summer favor root growth and beneficial bacterial activity in the soil. High summer temperatures may injure these microorganisms as well as the roots near the surface of the soil. In winter, frost penetration is less likely to occur in a mulched area. Evergreens must absorb moisture in the winter as well as summer; therefore, a winter mulch can prevent the soil water from freezing and becoming unavailable to plants.

Organic matter used as a mulch can improve soil structure and tilth. As it decays the mulch material works down into the topsoil. Decaying mulch also adds nutrients to the soil.

Mulching material, such as pine bark or pine needles, improves the appearance of the garden. It is valuable for covering beds near the house or in areas where neatness is important.

Disadvantages of MulchingThere are a few disadvantages to mulching.

First, the cost of some materials can be a drawback to large-scale mulching. Also, some mulches are not readily available.

When using sawdust and wood chips as a mulch, nitrogen starvation sometimes occurs, but this is easily corrected by using additional nitrogen.

Heavy mulching over a period of years may result in a buildup of soil over the crown area of the plants. This condition is especially harmful to camellias. After 3 years, it may be advisable to rake off the old mulch before applying a new layer to prevent plant roots from developing in the mulch material.

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Kerry Smith, Extension Home Grounds Program Coordinator. Originally prepared by J. David Williams, former Extension Horticulturist, and Ronald L. Shumack, former Extension Horticulturist, all with Auburn University.

For more information, call your county Extension office. Look in your telephone directory under your county’s name to find the number.

Published by the Alabama Cooperative Extension System (Alabama A&M University and Auburn University), an equal opportunity educator and employer.

9M, Reprinted Aug 2010, ANR-0385© 2010 by the Alabama Cooperative Extension System.

ANR-0385

MULCHING MATERIALSMaterial Depth to Apply Remarks

Rotted Manure 1 to 2 inches May contain weed seeds. Should be well composted to prevent burning plants.

Sawdust 1 to 2 inches Low in plant nutrients. Decomposes slowly. Tends to pack down. Wood Chips 2 to 3 inches Well-rotted materials preferred. Can be used fresh if ammonium Wood Shavings 2 to 3 inches nitrate is supplemented at the rate of 1 pound per 100 square feet. Keep away from building foundations; can attract termites.

Ground Corn Cobs 2 to 3 inches Excellent for improving soil structure.

Pine Needles 3 to 6 inches- Will not mat down. Fairly durable. Great for winter protection on perennials.

Peanut Hulls 2 to 3 inches Supplies plant nutrients and improves soil structure. Fairly durable. May contain nematodes.

Whole Tree Leaves 3 to 6 inches Excellent source of humus. Rots rapidly. Relatively high in Shredded Tree Leaves 2 to 3 inches nutrients. Oak leaves especially valuable for azaleas, camellias, and rhododendrons.

Hay 3 to 6 inches Unattractive but readily available. Grass clippings tend to mat and Grass Clippings 1 to 2 inches can repel water if they dry out. Should not be applied deeper than 2 inches.

Hay Straw 6 inches Same as above, but lower in nutrients although furnishes considerable potassium.

Pecan Hulls 1 to 2 inches Extremely durable. Availability limited. Will stain concrete.

Gravel 1 to 2 inches Limited use but particularly good for rock garden plantings. Stone Chips 1 to 2 inches Extremely durable; holds down weeds but does not supply plant nutrients or humus.

Newspaper 1⁄2 to 1 inch Good in open woodland, particularly under pines, to control weed growth. Should be covered with another mulch to improve appearance and prevent scattering.

Bark 2 to 3 inches Ground and packaged commercially. Especially attractive in this form.

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