Mulch & Bark Overview

  Basic Types of Mulch and Ground Cover

Natural Mulch is uncolored and not treated chemically in any way. There are many types of natural mulch. Natural mulch’s color varies by the age of the material, type of wood, and moisture content. Natural mulch is usually very economical. The material can last up to three years before becoming mostly decomposed. The color of natural mulch usually lasts 1-3 months after being applied. After natural mulch loses its fresh look, it will be dull-gray in color. It also does an excellent job of retaining soil moisture and prohibiting weed growth during one landscaping season.

Types of Natural Mulch Commonly used in the Landscaping Industry
include the following

Shredded Bark is the exterior of trees that is peeled off by lumber mills. The color and texture of bark also vary with the age of the material, species of tree the bark is from, and moisture content. The color of shredded bark usually lasts 1-3 months before turning dull-gray in color. The decomposition rate is high due to high moisture content along with typically finely shredded texture.

Tree Grindings, Stump Grindings, and Brush Grindings are terms used usually referring to the same type of natural mulch. This type of material is usually a by-product of land clearing. Brush, tree stumps, and trees can be ground into usable products. The color of the material can range from blonde to black depending on dirt content, types of material, age, and moisture. The color of these types of mulch usually lasts 1-3 months before turning dull-gray. The rate of decomposition is high due to high moisture content along with typically finely shredded texture.

Whole Tree Chips are another type of by-product usually coming from land clearing sites. The material is usually blonde in color and contains little dirt. Chip size can vary but are most common from 2”-5” in diameter and are usually less than 1 ½” thick. The decomposition rate is medium due to the material’s typically larger size and high moisture content.

Industrial Waste Wood Grindings are made by recycling reclaimed industry waste into a usable product.  Recycled industrial waste wood can vary in size and color, depending on the manufacturer’s methods of recycling, species of wood, age of the material, and moisture. The decomposition rate is slow due to very low moisture content.

Colored Enhanced Mulch is a manufactured product. It is produced by mixing some type of natural mulch with colorant. Colored mulch can be manufactured in any color. Unlike natural mulches, colored mulch loses its color only when it is manufactured incorrectly, endures high moisture contact (such as heavy rain or melting snow), or extremely high UV rays (most common in the southwestern United States). Colored mulch’s decomposition rate is usually slow but can be high depending on the type of natural mulch it is made from. Weeds capable of growing through the mulch can easily be dugout. After the mulch is decayed, it can be left as a soil additive, replaced, or the composted product easily dugout.

Rubber Mulch is made from worn tires. Like colored enhanced mulch, rubber mulch can be manufactured in any color. Different textures are also available. Rubber mulch can be chipped up to appear similar to round, flat chips made from wood. Rubber mulch can also be shredded to look stringy. Rubber mulch does not decay. This makes disposal of the material difficult if landscaping alterations are desired. Weeds can grow through the material after it is applied.

Properties of Mulch

Mulch is produced by reducing any organic material. The landscaping industry usually refers to some type of shredded, ground-up, or chipped-up material when using this term. Shredded bark, wood chips, stump grindings, ground-up lawn debris, even ground-up rubber tires are different types of mulch. Primary functions of all types of mulch include retaining soil moisture, controlling soil temperature, and inhibiting weed growth. Some types of mulch are used for decorative applications. The types of mulch differ from each other in texture, color, applications, and longevity.

Trends in the landscaping industry change. Homeowners and businesses originally used stone and rock to control weeds and retain moisture. Eventually, the trends changed to shredded bark and other organic material that could decompose over time. By using material that can be decomposed, landscapes could easily be altered. Organic material could be left to decompose in landscape beds or shoveled onto compost piles when alterations were desired. Non-decomposing material limits the ease of change through difficult disposal of the material.

The longevity or decomposition of mulch is affected by moisture content, size, and application (such as depth applied). Mulch with higher moisture content decays quicker than mulch with little moisture content. Likewise, mulch which is reduced more in size decays quicker than mulch less reduced in size. Mulch that is applied thicker retains more moisture; the moisture makes the material decompose quicker than material applied too thin to hold any moisture. How long the functions of mulch lasts varies for each type of mulch.

Mulch Textures vary for each type of mulch. Shredded material may appear like broken pencils while chipped material often refers to the round, flat chips. Each type of mulch texture influences the characteristics of the mulch. Typically, shredded mulch blows less in windy situations than chipped mulch. Shredded mulch also resists flotation more than chipped mulch. Shredded mulch resists these situations better because shredded material tends to intertwine together after settling has occurred.

Flotation can be a concern when purchasing mulch. The best way to prevent mulch flotation is to have no areas in landscaping beds that may hold standing water. Washouts may also be a concern. Washouts occur most often under areas located directly under roofs with no rain gutters. The high flow of water onto a certain area can push the material into an area where mulch is not desired. Washouts can be easily corrected by having proper water drainage off roofs. Landscape edging can help prevent mulch from washing onto lawns, driveways, or walkways.