Much More on Mulch

More Mulch Tips

  • To determine the amount of mulch needed, measure the bed areas and multiply the width times the length to arrive at the square footage. One cubic yard of mulch will cover 324 sq. ft to a depth of an inch. One cubic yard of mulch will provide a 3-inch layer for 108 sq. ft.
  • Mulch in fruit and vegetable gardens reduces spoilage by reducing contact of fruit/vegetable to the soil.
  • Topdressing turf areas with ½” to ¾” of compost spring and fall is an effective mulch for lawns.
  • Mowing with a mulch mower, well, mulches the lawn. Simplest and easiest way to mulch the lawn, and mow at the same time. Saves time, money and water! No more bagging, and dumping lawn clippings in landfills. No more clippings to compost either, unless you just periodically decide to compost a few bags.
  • Mulching within the tree drip line is beneficial to trees by eliminating competition for available water and nutrients. Removing turf from this area and placing 2-4 inches of mulch allows for air and water exchange into the root zone. A mulched tree ring will greatly discourage weeds and turf from growing up to the trunk.
  • Mulching around trees reduces mechanical damage. Many trees are severely injured by weed trimmers. Our climate is hard on trees; try to provide them every advantage. ( Mulching around a tree is one of the most beneficial things a homeowner can do for the health of the tree, according to the International Society of Arboriculture (
  • If your organic mulch develops a mold, stir the mulch cover to allow the mulch to dry faster. This may happen if mulch is kept too wet.
  • If your soil is already rich in organic content, nitrogen deficiencies due to mulch will not occur. The bigger and thicker the mulch, the longer it will take to decompose. This fact should be balanced with the look you desire and your time available for replenishment of the mulch layer.
  • Sawdust is very fine, high-carbon mulch and could rob the soil temporarily of nitrogen and is not generally recommended, unless used to mulch pathways.
  • When replanting in a bed mulched with wood chips or wood bark, first clear the planting area of the mulch before digging. Try to avoid wood chips or bark from falling into the planting hole. Similar to sawdust, bark and other high carbon materials create temporary nitrogen deficiencies when decomposing.
  • If your home is on the range and wind is the king, lay down finer mulch first, then a much larger, heavier mulch or thick bark mulch. Wind and our sporadic torrential rain will displace mulch in country locations. If you want to use organic mulch and wind is still a problem, put mulch down, then cover and stake down with a porous, water and air permeable fabric.
  • Mulch needs periodic replenishment. The frequency depends a lot on the available rainfall, irrigation practices and type of mulch. Organic mulch decomposes faster with more moisture in our dry climate. Thin grass blades decompose much faster than bark or wood chips. Inorganic mulch works it’s way down into the soil after several years and will also need replenishment.
  • When mulching a new planting bed, it'll look like more mulch than plants. As the plants grow and spread, they should knit together and shade the soil. If depending on living mulch cover, adding mulch is still recommended between plants for all the benefits cited earlier.
  • When mulching plants, in our dry and low-humidity area, we are not overly concerned with fungal diseases developing from mulch placed next to the crown, stem or trunk of plants. It is still good practice to keep the mulch cover off plant stem or tree bark. We can keep our beds covered with mulch over the winter, unlike the rainier and more humid climates. But don't mulch too high or pile up mulch more than 6 inches—3-4 inches is usually sufficient. Too thickly applied mulch hinders the exchange of gases. Fresh grass clippings should be used in only a thin layer or composted before using as mulch. When applied fresh, it mats together creating a barrier to air and water.
  • For aesthetic purposes, it is best not to combine different mulch types in the same bed.

Mulch Insights/Cautions

Mulch is not a cure all for our landscape problems. You might entertain a misconception about mulch; I hope to clear that up here. Sometimes, mulch applied incorrectly or wrongly can be damaging to plants, landscape and perhaps even your home.

  • Mulch does not reduce weed infestations if weeds are already present.
  • Mulch does not eliminate plant disease or reduce insect attack. However, some of the benefits of mulch create more favorable growing conditions that reduce pathogen and insect attack.
  • Insure that your mulch is weed and pest free.
  • Mulch is not a substitute for adding organic matter to your soil.
  • Do not use leaves, plants or other materials that have been sprayed and/or treated with an herbicide or pesticide.
  • To avoid a termite problem having to do with mulch, do not use a wood mulch product next to your home or other buildings.
  • Avoid wood chips and bark from pressure treated, arsenic or chemical soaked pallets, landscape timbers, railroad ties or other undesirable wood. Do not burn these items.
  • Avoid wood chips with a sour smell, similar to vinegar.
  • Cocoa bean hulls, or cocoa hulls have a nice rich brown color and chocolate smell. But the hulls contain 2 compounds that are toxic to dogs. Even consuming small amounts by dogs can be lethal (for more information, click on Cocoa hulls).
  • Don't mulch too high or pile up mulch more than 6 inches (except in vertical mulching).
  • Do not mulch right up to the stem, trunk or crown of a plant, especially trees.
  • Sawdust is a very high-carbon material and could rob the soil temporarily of nitrogen and is not generally recommended as mulch in a bed or border, unless used to mulch pathways. It’s better to turn the sawdust into compost first.
  • When replanting in a wood chipped or bark mulched bed, do not let wood chips or back fall into the planting hole.
  • Do not use fresh manure as mulch. Compost it first.
  • Do not use rubber mulch in landscape beds or borders. Do not even compost rubber mulch.

Mulching for Cold Hardiness and Wind Barriers

Although moderating soil temperatures in the summer and water conservation are two primary benefits of mulching, different mulch types and techniques also protect plants during the cold winter and windy spring months.

The use of mulch aids the gardener in expanding plant selection. We often desire to grow plants that are labeled with a USDA Cold Hardiness Zone warmer than our climate or microclimate. Mulching with thicker layers during the winter, from 4 – 12 inches, can stretch the cold hardiness by ½ to a full zone. In other words, the roots of your plants will be protected an additional 5° to 10° regardless of the microclimate with this increased layer of winter mulch.

This thick, mulch layer should be layered for a distance at least 1 – 2 feet from the trunk or stem for a small plant and several feet for a larger tree or shrub. The thick mulch will help prevent the ground from freezing, or freezing deeply, and allowing the roots to access soil moisture. (Palms Won’t Grow Here, Francko, Timber Press, 2003.)

Thicker layers need only be used in an attempt to extend the cold hardiness of tender perennials you wish to winter over. Thicker wintertime mulch has the same effect for southwestern gardeners, as does a thick and constant snow cover for northern landscapes. Mulching during the Panhandle’s volatile spring and fall seasons moderates the rapid and widespread temperature shifts that are one of our most damaging extremes.

To extend the cold hardiness beyond this range takes more extreme measures. Gardeners in more northern climates often will heel in their roses and other tender perennials by tipping or angling them severely so as to bury them.

Vertical Mulching

Another technique used to help prevent or minimize stem freezing, is a technique called vertical mulching. Erect a wire cage (usually chicken wire) around the plant with a radius of 1 – 2 feet and fill it with leaves or coarse wood chips (thick coarse leaves are best). Inside the cage, wrap the plant with plastic or row cover fabric to avoid mulching right up to the stem. In moist areas, spraying the plant stem with a broad-spectrum fungicide /bactericide will help prevent a pathogen problem. Your goal is to protect the tender bud tissue that is necessary for recovery from catastrophic cold (this temperature varies with the plant species). Mulch up 4 – 12 inches, or in some cases, the entire height of the plant. In windy locations, wrap the outside of the cage with row cover fabric to hold in the mulch better. This type of mulching will help prevent the soil freezing around the plant as well as protecting against stem freezes.

Vertical plant protectors, Wall-O-Waters, protect tomatoes and other tender plants. This is a type of vertical mulching that many gardeners use in springtime to moderate colder nighttime temperatures, enabling them to plant sooner in the season. The plastic tubes are filled with water and heated by the sun by day. At night, as the water cools, heat is released and protects the plant from freezing.

Row Covers, Grow Webs

Row covers, sometimes termed floating row covers, are still another form of mulch, except above the ground and plant. This type of material is used to warm the soil, moderate temperatures, wind and insects. Different materials for row covers include perforated polyethylene and spun bound polyester or polypropylene and they are available in several weights.

Row covers are placed over the transplants or seeded beds and anchored down on the sides to prevent damage to the plants by flapping in the wind. A secure fit is necessary to entrap heat and serve as a barrier to wind, insects and other critters. It is water permeable. Sunlight also passes through, but the light intensity varies as to the thickness of the row cover.

The greatest benefit of heat entrapment is realized in the fall months due to warmer soil temperatures, when attempting to extend the growing season. In spring, I use row covers to start lettuce and radish beds in February. Snow falling on row covers does no damage, unless the snowfall is very heavy and later in the season when the plants have emerged to a taller height (snow can fall as late as May). I’ve found row covers greatly reduces evaporation and desiccation of the tender seedlings by our terrible spring winds. Tomato or any other larger plant can be caged and wrapped with the grow web material as a wind barrier as well. The row covers, or grow webs, should be removed as the plants’ soft, tender tissue hardens.

Mulching for Water Conservation

Mulching beds and borders is an effective tool in the conservation water. Soil moisture is conserved by mulch in a number of ways:

  • Mulch reduces evaporation and retains moisture in the root zone.
  • Mulch moderates soil temperature. During the hot summer months, mulch cools the soil. Plants require less water due to the cooler soil temperatures when mulched.
  • Mulch prevents soil crusting and promotes in soak of water. Rainfall and irrigation is used rather than runs off.
  • Mulch prevents soil compaction from heavy rainfall. Mulch on pathways reduces soil compaction. Lack of compaction promotes better soil drainage.
  • Mulch minimizes cultivation. Organic matter slowly adds humus to the soil. Reduced cultivation and increased humus increases the soil microbial life. Soil microorganisms help create better soil structure through their secretion of sticky gums. Soil with improved soil structure captures and holds water in the soil better.

How Mulch Helps to Overcome our Extreme Conditions and Climate

Although each of these mulch benefits that aid in moderating extreme climate events or soil conditions may seem minor, taken together as a whole, your garden’s appearance and health will improve with minimal effort and minimal yearly maintenance. When combined with the benefits from implementing the other six basic principles of gardening, the result is a beautifully thriving, low water-use, ecologically friendly and lower maintenance garden.

  • Mulch conserves water by reducing evaporation and improving the soil structure.
  • Mulch helps retain water in the root zone and promotes in soak of rainfall.
  • The structure of sandy soil and compacted, clay and caliche soil is improved over time through the decomposition of organic mulch. Cover crops turned into the soil increases the organic content of the soil.
  • Reduced germination of wind-borne weed seeds.
  • Mulch moderates soil temperature from daylight to night, and during the hot summer, insulates similar to snow cover in northern climates during the cold winter months, and helps to protect the soil organisms and plant roots during rapid temperature shifts.
  • Prevents soil crusting and compaction brought on from periods of drought and hard driving rain.
  • Reduces erosion by wind and hard rain.

Nature’s Mulch

In the absence of the gardener’s intervention, or provident native plants, and if conditions exist at all to encourage germination and sustain life, weeds spring up. Not, weeds may spring up, weeds will most certainly spring up. Unwanted, invasive, industrious, tireless, fertile weeds. At best, a “volunteer” seed may sprout from some desired or highly prized garden specimen in vacant and uncovered soil, but these occurrences are rare and treasured, in comparison to this act of nature we all grouse about. If as gardeners, we wish to garden more efficiently, mulch to circumvent the natural order of things.

Advocates of weeds exalt their many benefits, particularly their ability to bring up nutrients from lower depths to the top. Weedy vegetation, too at season’s end, dies and eventually becomes mulch, then compost. In locations damaged or deprived beyond the redemption brought by benefit of weeds, the alternative is baked, cracked clay, sandy dunes and caliche pits, utterly bereft of soil moisture, organic and mineral materials and the necessary soil structure to support life.

Angie Hanna, July, 2006