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Everything You Need to Know About Mulch The "executive summary" or "abstract" is: Mulch is simply stuff you spread just 2 to 2-and-a-half inches thick, providing multiple benefits, covering the surface of the soil under and around plants, but not actually touching their stem or trunk. We could call spreading mulch, the act of "mulching." Among the many benefits of mulching are: preventing weed growth conserving moisture in the soil* insulating the soil surface, cooling it in hot weather, yet also keeping it warm in cold weather * reducing "heaving" (plant roots forced upward out of the soil) of small plants as a result of alternate freezing and thawing of the soil in autumn, winter and spring* adding organic matter to soil if organic mulch materials are used (as well as the exercise and fresh air you get when you have to add to the mulch every few years) reducing soil erosion on slopes keeping the plants above cleaner, especially good for fruits, vegetables and flowers adjusting the pH of the soil below the mulch (over time, that is) improving the aesthetics of a landscape, adding to property values * Research by the Weyerhaeuser Company (1969) indicated that two inches of bark mulch: 1) reduced moisture loss in summer by 21 percent, 2) reduced soil temperature in summer, down to as much as four inches deep in soil by 10 degrees F, and, 3) delayed soil temperature rise at the onset of winter from reaching freezing by two days compared to unmulched soil. Effects of Organic Mulches in Soil Organic mulches, derived from plant material, will decompose in time and enrich and improve the soil. Different materials will, understandably, decompose at different rates, but you do have to add to natural mulches by the third year after it's been applied. Decomposition results in increased aeration for silt or clay loam soils and added water-holding capacity for porous sandy loam soils. Mulching improves and stabilizes soil structure (the arrangement of soil particles) by reducing the impact of rain, weight (even people walking on the soil, but especially garden tractors, etc.) and reducing the impact of cultivation of soils, especially when wet. In short, compaction of the soil is reduced. The pH (acidity or alkalinity) of soil can be changed depending on the mulch selected. For example, most composts will be slightly alkaline (pH greater than 7) and excellent for use in acidic soil regions, while the continuous use of oak leaves, pine needles, pine bark and sphagnum peat moss will increase acidity. The chemical breakdown products of leaves, including oak leaves, will be alkaline, but surprisingly, continuous use of oak, pine and sphagnum peat moss products will keep the soil surface acidic (pH less than 7). Go figure! Organic mulches contain both major and minor mineral elements essential for plant growth, but should not be considered substitutes for fertilizer. In fact, materials such as straw, wood chips and sawdust have high carbon to nitrogen ratios; and therefore, nitrogen must be added to the soil at the time of mulching. The high carbon to nitrogen ratio materials are easily decomposed by microorganisms. The microorganisms require nitrogen to multiply and survive. As a guide, 1 to 2 pounds of actual nitrogen per 1,000 square feet should be applied to all soils used for typical landscape planting. For example, if using a 10% nitrogen fertilizer, such as a 10-6-4, applying 1 pound nitrogen to 1000 square feet would require 10 pounds of the fertilizer product. If additional nitrogen is not supplied, the nitrogen in the soil will be used by the microorganisms in the root zone of desired landscape plants, and nitrogen deficiency will likely occur. Plants won't necessarily die without such fertilizing, but their growth and beauty will be impaired. Timing the Application of Mulches Any time a new tree or shrub, etc. is planted, mulch should be applied IMMEDIATELY. Just as soon as you can, spread your mulch around what will be the base of your mature tree as it grows up and grows out. For existing trees and planting beds, mulch is usually applied first in spring after the soil has warmed and begun to dry from winter's snow and rain. Depending on soil texture (size of soil particles, e.g., clay [teeny tiny small]; silt [medium, for a soil]; and sand [large, you can actually see these particles as sand grains]), temperature and other weather conditions, this is usually mid to late spring. Mulching too early can delay drying of soil and subsequent root growth which is dependent upon sufficient aeration (oxygen content in soil) and reasonably warm temperature in the root zone. In seasons of more than ample rainfall and/or cool temperatures, mulching should be delayed until late May or June. Not to worry, if you are off by a week or two, you're still doing your plants oodles of good; not to worry, perfection is a goal not often achieved in any endeavor. A second application of mulch, not an entire mulching, just to add some more, is often needed in autumn. For established plants, timing of the mulch application may not be as important as it is for new plantings, especially shallow rooted shrubs and evergreens, herbaceous perennials, or strawberries. Wintertime heaving of small plants, especially those newly planted, occurs following alternate freezing and thawing of the soil. To reduce heaving, which breaks roots injuring their plants, apply mulch following the first indication of frost in the ground. Mulching slows the thawing cycle and thus root heaving. For established plants, water thoroughly in late autumn if the soil is not already moist, and then mulch. Mulching Depth The recommended mulching depth, depending on the material selected, is 2 to 2-and-a-half inches. At this depth, most mulches will accommodate the primary objectives of weed control, soil moisture conservation and temperature modification. "Meps. Meps! Unacceptable!!" This was the refrain of the 1980's and 90's comedy sketch from the television show Saturday Night Live, known as SNL. "We are the Coneheads," the comic actors would proclaim. "We are from France. We have been sent from the planet Remulak to subdue the Earth and make it a minor refueling location..." When applying mulch, don't be a conehead! Remember, it is "unacceptable" to make a high cone piled up around the base of your trees. "Meps!" Make it essentially FLAT. Some years ago at some state capitol building grounds, a crew of temporary summer workers were given a truckload of mulch to do the trees. They believed they were expected to use up all the mulch which had been brought. The youngsters didn't know better and wanted to do a good job, so they kept busy and used every last shred of mulch piling it high around every tree in a cone-shape. Time didn't allow for the regular staff to remove the extra mulch and so the conelike piles remained, a foot deep on the base of the tree trunks. It was done WRONG! When landscapers and gardeners, etc. passed by and saw this, they erroneously, as in bi-i-g mistake, thought that the head groundskeeper or official state gardener must know something new about mulch. Too many people copied the very bad conelike piling of mulch because that's how it got done one time at a state capitol, and then they told all their friends and their friends told their friends and so the notion spread like wildfire, like a virus, just like gossip. We see too many examples of this around our area of southeastern Pennsylvania. If you can, explain the story to people who continue to make this mistake and please don't make the mistake yourself! Make a sort of flat doughnut shaped ring with the mulch, similar to the shape of a "senso ring" from the comedy routine. Leave the first few inches immediately surrounding the base of the tree bare, mulch contacting bark damages it. Spread a layer about two inches to two and-a-half inches thick outwardly several feet, or more, depending on the size of your tree. Then, at the outermost circumference build up the mulch into a berm. Make it about double thickness, maybe 5 inches high. This berm will be like a levee, or dam, to contain water from either rainfall or if you use your garden hose. Remember the rule of thumb for how much to water: New trees need at least an inch of water per day for the first few months. If this is kept up for a whole year, the root system will be the deepest and widest possible. An inch of water is 5/8 of a gallon per square foot. That's OVER a half gallon for every little 12 inches by 12 inches of area. Wow. Mulching itself is easy. Just shovel, or pour, and spread. It's as easy as taking a driving lesson From "Beldar Conehead." Really. Organic Mulch Products Animal Manures. Historically, manure has been available from farms in bulk, but some are packaged for retail sales. Farm manure, when aged a few years will have no odor, but cows do NOT digest seeds, so the especially hardy weed seeds will be introduced to your soil. Plain rabbit manure is especially rich in the big three elements, Nitrogen, Potassium, and Phosphorous. Don't use chicken manure which is low in N-P-K and has too much ammonia. The bad odor indicates it is foul! (punny, huh?) Manures are often dried or dehydrated and granulated to be sold for soil amending, mulching, or fertilizer purposes. Still, weed seeds are often introduced with manure. Included in retail packaging are manure from cow, horse, sheep, poultry and zoological (zoo) animals. Composts. This is an old term with new meanings as compost technology and new products become available. Although usually not packaged for retail use, grass clippings, leafmold and used mushroom composts are available. There's the added benefit here of knowing you're helping recycling. Composted municipal sludge. Sometimes available from your town or city government, even for "free," also given trade names like Earthlife, Comtil and TechnaGro. Composts containing municipal garbage, paper pulp, yard wastes and many other by-products help reduce the amount of landfill necessary. Again, this is helpful recycling. Environmental laws across the United States have given rise to composting technology that continues to advance and bring new products. Hulls, cobs, shells. This group of by-products, to a large degree from the food industry, includes such mulches as cottonseed, buckwheat, cocoa-bean, peanut or rice hulls, crushed corn cobs, spent hops, tobacco stems and similar products. All have been used extensively for mulch and are usually inexpensive. The disadvantage is that availability is typically limited to a local area. Sphagnum peat moss/muck peat. These terms are often misunderstood. Sphagnum peat moss comes from sphagnum and similar mosses. It contains long fibers which resist decomposition. It is available from Canada, Russia, Ireland and much of Europe. Note - Spanish Moss which hangs from trees in the swamps of the southeastern United States and all the way down to South America, is NOT moss, it's actually an air-plant, or epiphyte. Chiggers, or redbugs, live in Spanish Moss, so maybe using this free mulch wouldn't be such a great idea... Use free grass clippings, bark, leaves, and the like, instead. Muck peat originates from well decomposed plant material that once thrived in swamps. Cattails, reeds, sedges and other water plants become muck peat. While sphagnum peat moss is usually quite acidic, muck peat is usually neutral to slightly alkaline, is well decomposed and is dark brown or black with almost no fibers. Muck peat is available from sources in many states including Pennsylvania, New Jersey, New York, Delaware, and Maryland. It is fine in texture, so it dries quickly and has the disadvantage of being blown away by high winds when used as a mulch. It, too, is often locally available at a reasonable price. Muck peat makes a far better organic soil amendment for rocky and sandy soil than a mulch. Pine needles. The needles of pine trees as well as shredded cones make an excellent mulch particularly for other evergreens and plants that thrive in acidic soils. Pine needle mulch, formerly available only in the southern states, is becoming available in other regions. The adavantage of this mulch is the acidity and pH adjusting capability for overly alkaline ("basic") high pH soils. Soils derived from limestone, because of the calcium carbonate (CaCO3) sea shells, are very alkaline, certainly well above a pH of 7, as much as 8 and higher. Straw. Straw and hay are used for winter protection of perennials, strawberries and small plants. If left as a permanent mulch, you'll need to add additional nitrogen (one pound of nitrogen per 1,000 square feet). This material decomposes readily. read this as, this material has to be added to every year for certain. Weed seed can be introduced from straw, hay and grain crop residues also. Salt hay, available along coastal states, makes the best hay mulch, very acceptable. Wood products. For simplicity, we will group all wood products into a) shredded, chip or chunk bark, b) wood chips or shavings and c) waste wood. Shredded, chip, or chunk bark. This material is by far THE MOST POPULAR landscape mulch due to its appearance, serviceability and cost. Included are shredded hardwood and cypress bark, chipped and chunk pine, and fir and eucalyptus barks. Wood chips or shavings. These have become available very inexpensively through utility companies and are usually not available in packaged form. You can make your own if you have a chipper-shredder for the downed trees and limbs on your property. Since these mulches consist, along with sawdust, of more wood than bark, they decompose rapidly and should be reapplied annually while also supplemented with fertilizer at the rate of one pound of actual nitrogen per 1,000 square feet of mulched area as mentioned above. Waste wood. Materials such as used pallets and other wood pieces that normally would have been taken to a landfill are now shredded and metal objects are removed. The resulting chips are colored to match pine, hardwood, cypress or any other mulch product on the market. This material also decomposes faster than bark and requires the addition of nitrogen fertilizer along with more frequent reapplication. It's good recycling however. If you've read this far, now you know all you'll ever need to about mulch and "mulching." Pat yourself on the back!

About the Author

Bill has been raising trees for 30 years at his Doylestown Pa. Farm and has a web site http://www.digatree.com