Mulching

    Scope Images
    Image
    Mulch can provide many benefits to a landscape.
    Scope

    Cover all exposed soil with a 2- to 3-inch layer of mulching material. Mulch can provide many benefits to a landscape, including reducing the evaporation of water from the soil.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

     

    Description

    Mulching has numerous beneficial effects upon the soil and plants, including:

    • Preventing loss of water from the soil by evaporation. Moisture moves by capillary action to the surface and evaporates if the soil is not covered by mulch.
    • Suppressing weeds when the mulch material itself is weed-free and applied deeply enough to prevent weed germination or to smother existing small weeds.
    • Maintaining a more uniform soil temperature. The mulch acts as an insulator that keeps the soil cool under intense sunlight and warm during cold weather.
    • Preventing crusting of the soil surface, thus improving absorption and percolation of water into the soil and, at the same time, reducing erosion.
    • Improving soil structure by using organic materials as mulch. As mulch decays, the material becomes topsoil. Decaying mulch can also add nutrients to the soil.
    • Increasing the beauty of the landscape by providing a cover of uniform color and interesting texture to the surface.

    Healthy soils effectively cycle nutrients; minimize runoff and maximize water holding capacity; absorb excess nutrients, sediments, and pollutants; and provide a healthy rooting environment and habitat for plants. Preserving existing topsoil, adding organic material, and minimizing compaction are practices that allow soils to function as a base for large, healthy plants that require fewer pesticides, fertilizers, and supplemental water for plant growth. Healthy soils also maintain a permeable soil structure, which ensures higher water infiltration rates that in turn reduce erosion, runoff, and flooding potential.

    Mulch can provide many benefits to a landscape, including reducing the evaporation of water from the soil.
    Figure 1. Mulch can reduce erosion and help retain moisture. (Source: U.S. EPA WaterSense Program.)

     

    Mulch can provide many benefits to a landscape, including reducing the evaporation of water from the soil.
    Figure 2. Stone mulch provides a pervious walking surface while retaining moisture and minimizing erosion. (Source: U.S. EPA WaterSense Program.)

     

    Mulching is an extremely important practice for establishing plantings, as it helps to conserve moisture in the root ball of the new plant until it establishes roots in the adjacent landscape soil. Mulch also helps discourage weeds that can compete with new plantings for water, nutrients, and light. Mulch can be used instead of grass around individual trees and shrubs in a lawn. This greatly reduces the competition for water and nutrients from the turf and increases the growth rate and health of trees and shrubs. In addition to being useful around plants, mulch can be used as a groundcover for walks, trails, driveways, and natural and play areas. It can be used temporarily to cover low-growing tender plants to protect them from frost injury. Mulch also can be composted and used as a soil amendment. For trees, at a minimum, mulch should be applied to the area below the tree’s canopy from the tree base to the drip line, or the border of the canopy of the tree, leaving space between the beginning of the mulch layer and the tree trunk to prevent rot.

    Too much mulch, however, can create problems. Because mulch helps retain moisture, too much mulch can lead to excess moisture. Especially in trees, this can lead to root rot. Do not pile mulch against the stems of plants or the trunks of trees, as this can cause stress on the plant tissues and lead to pest problems. Too much mulch can also alter the pH of the soil, causing toxicities or deficiencies. Piled mulch provides a home for rodents, which in turn may chew the plant roots and cause tree girdling. Fine mulch can become matted if applied too thick, preventing air and moisture penetration.

    Ensuring Success

    The inspector will verify that all mulched areas are between 2 and 3 inches deep and that there are no areas of exposed soil in the landscaped area.

    Mulch entire beds of shrubs, trees, annuals, perennials, and/or ground covers. For the purposes of this specification, mulch is defined as a permeable arrangement of organic and/or inorganic materials that will retain soil moisture, suppress weeds, and allow free movement of oxygen into and out of the soil. For example, organic mulches include wood-based materials such as wood chips or bark, while inorganic mulches include rock-based materials such as pea gravel or lava rock. Artificial turf is considered mulch for the purposes of this specification, provided that it meets the definition.

    Make sure mulch is at least 2 inches, but no more than 3 inches deep. When complete, the landscape should not have any areas of exposed soil. Additionally, the landscape professional should take measures to prevent on- and off-site migration of mulching materials to sidewalks, streets, etc.

    Climate

    Install climate-appropriate mulches.

    Right and Wrong Images
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    Right - Lawn clippings were placed evenly to create a layer of mulch around the garden.
    Right - Lawn clippings were placed evenly to create a layer of mulch around the garden.
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    Wrong - Volcano mulching harms trees and wastes mulch by piling it up the trunk of a tree where moisture can cause rot.
    Wrong - Volcano mulching harms trees and wastes mulch by piling it up the trunk of a tree where moisture can cause rot.
    Image
    Right - This tree has been given space around the roots to allow for proper growth and expansion of the tree over time.
    Right - This tree has been given space around the roots to allow for proper growth and expansion of the tree over time.
    Image
    Right - Mulch covers the empty spaces in this garden, retaining moisture, moderating temperatures, and providing nutrients as it decomposes.
    Right - Mulch covers the empty spaces in this garden, retaining moisture, moderating temperatures, and providing nutrients as it decomposes.
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    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    Environmental Protection Agency (EPA) WaterSense® New Home Specification

    The EPA WaterSense New Home Specification states that:
    All exposed soil shall be covered with a 2- to 3-inch layer of mulching material.

     

    Environmental Protection Agency (EPA) WaterSense Inspection and Verification Guidance for WaterSense Labeled New Homes

    The EPA WaterSense Inspection and Verification Guidance for WaterSense Labeled New Homes states that: 

    Mulching material is defined as a permeable arrangement of organic and/or inorganic materials that will retain soil moisture, suppress weeds, and allow free movement of oxygen into and out of the soil. Artificial turf is considered mulching material under this specification.

    Existing Homes

    Guidance for the measures described in this guide is applicable to both new and existing homes.

    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    References and Resources*
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    PDF detailing the inspection and verification guidance for WaterSense labeled new homes including indoor and outdoor efficiency requirements, and homeowner and building management education.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Resource to help builders better understand the WaterSense requirements for labeled homes and assist them in meeting the criteria so they can receive the label for their new construction.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Resource that provides a checklist of program criteria for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Resource that establishes the criteria for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.
    Author(s)
    EPA
    Organization(s)
    U.S. Environmental Protection Agency
    Publication Date
    Description
    Resource that provides a directory of individuals that have sucessfully completed all requirements of at least one WaterSense labeled professional certification program.
    Author(s)
    Fayetteville NC
    Organization(s)
    Fayetteville NC
    Publication Date
    Description
    Pamphlet describing proper mulching around trees and problems and benefits associated with mulching.
    Author(s)
    Robert J. Black,
    Edward F. Gilman,
    Gary W. Knox and Kathleen C. Ruppert
    Organization(s)
    University of Florida,
    Institute of Food and Agriculture Sciences
    Publication Date
    Description
    Resource that provides information about mulching materials and methods.
    Author(s)
    Sabata,
    United States Department of Agriculture
    Organization(s)
    USDA
    Publication Date
    Description
    Article describing mulch requirements and benefits.
    Author(s)
    Garden City Harvest
    Organization(s)
    Garden City Harvest
    Publication Date
    Description
    Article describing mulching with lawn clippings.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Guide describing landscaping tips for healthy and regionally-based gardens, including maintenance, mulching, water efficiency, and plant resources.
    Author(s)
    University of Tennessee
    Organization(s)
    University of Tennessee
    Publication Date
    Description
    Pamphlet describing different types of mulches and their benefits.
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

    Building Science Measures
    Building Science-to-Sales Translator

    Efficient Landscape Design = Water Saving Landscape Design

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    Technical Description

    Landscaping irrigation needs can be reduced or even eliminated by choosing native, drought-tolerant species that can survive on available rainfall and by installing non-plant ground covers like rock and bark. If there will be plants that require irrigation, they can be planted in clusters for efficient irrigation, while the remainder of the yard receives little or no irrigation.

    Water Saving Landscape Design
    Sales Message

    Water saving landscaping use drought-resistance tree, plants, and shrubs to substantially reduce water needed for irrigation. What this means to you is the great feeling that comes from not wasting thousands of gallons of water needlessly each year along with money saved on water bills. Wouldn’t you agree water is too important to waste?

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