How to Choose the Best Type of Mulch for Your Project

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Mulch is a miracle of multitasking, and applying an insulating layer in the garden can accomplish many different goals. Different types of mulch offer different benefits—from adding curb appeal to improving the soil in your organic garden. The primary divide is between organic mulches (like pine needles) that decompose over time and inorganic mulches (like pebbles) that do not.

The type of mulch that works best for you depends entirely on your project and the purpose the mulch will serve in the landscape. Consider these 10 popular mulch options.

Using Compost for Mulch

Organic mulches are made of substances that were once alive. They decay into the soil, improving the soil structure and enriching it with nutrients. When it comes to organic mulch, compost is first among equals. It is essentially garden clippings and kitchen detritus allowed to decompose in a pile until it forms a soil-like substance.

Organic compost is often worked into a garden bed as a soil amendment. However, it can also be layered on top of the soil as a mulch. It works well as mulch for perennials, keeping the beds clear of weeds, retaining moisture and buffering temperature extremes. However, compost mulch needs to be replaced or renewed regularly, so add a layer every month or so throughout the growing season.

If you set up a backyard compost pile, you can get organic compost free of charge. Otherwise, buy bags of it at a garden supply store. Compost mulch looks like a layer of dark, rich earth, and it is attractive in flower beds and vegetable gardens.

Using Grass or Leaves for Mulch

Grass clippings and shredded, dried leaves are other inexpensive organic mulches. Gardeners collect grass clippings from their own lawns after mowing. The trick is not to use chemical fertilizers or pesticides on the lawn. Likewise, you can rake up fallen leaves in autumn and run them through a shredder. Ideally, the leaves should be stored and dried before using them as mulch.

Grass clipping mulch or shredded leaf mulch works well in vegetable gardens as well as flower beds. Apply the grass and leaf mulch in thin layers since thicker layers can form a mat and lead to rot. At the end of the growing season, these mulches can be worked into the soil to improve the soil's texture and nutrient content.

The big disadvantage is that these mulches are short-term fixes. They must be renewed seasonally at the very least, and rough winds can dislodge grass and leaf mulch quite easily.

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Using Pine Needles for Mulch

For plants that prefer acidic soil like blueberries, pine needle mulch (also called pine straw) is a very attractive option. It's natural and organic, and it increases soil acidity as it decomposes.

Unlike pebbles or even compost, pine needles are fairly lightweight, making them easier to layer as a mulch. Although they are organic and decay over time, they last longer than other organic mulches and only need replacing every five years or so. Pine needles used as mulch knit together, according to the University of Florida Master Gardener Program, making them unlikely to blow away in the wind.

Pine straw works well to regulate the soil temperature, insulating plant roots from highs and lows. They are a good choice for controlling erosion on slopes. Homeowners with pines can rake up their own supply, but the product is also available commercially, often harvested from natural needles. Since pine needles are flammable, they are probably not the best choice in dry, hot climates.

Using Straw for Mulch

Straw mulch is fairly economical and easy to use, making it a popular choice in the vegetable garden. While bales of straw are heavy, they are so compressed that, when broken up into lightweight flakes, one bail covers quite a large area. Straw is an effective type of mulch for maintaining soil temperature since it is porous.

Straw mulch can be made of rice straw, wheat straw or oat straw. The great advantage of rice straw is that it is seed-free, so you can apply a layer without treating it. However, it disintegrates rapidly in the yard. Both wheat and oat straw last longer but need to be soaked before using to kill their seeds. According to University of California Master Gardener Program of Sonoma County, you can either keep the bales wet until a few inches of grass sprouts or leave them outside in the rain for a month or so.

Straw mulch works well to mulch new lawns to protect the grass seeds. It also holds moisture in the soil and encourages worms that aerate the beds. If you don't like the way straw looks, you can cover it with a more ornamental mulch. Don't confuse straw with hay, which usually brings a profusion of weed seeds with it.

Using Bark/Wood Chips for Mulch

There are more than a few types of wood chunks that make good mulch. Commercially available wood mulch is sold aged and dried. This includes tree bark mulch (e.g., pine bark mulch), wood chips and wood nuggets (chunkier chips that are about 1 inch in diameter). You can even find them dyed black, brown or red at home improvement centers.

Wood chip mulch can be from hardwood trees (used around shrubs and perennial beds) or softwood, like pine, used around large trees. Pine is more acidic, so you should reserve it for acid-loving trees.

Wood mulch is neat and attractive in the landscape, is easy to transport in bags and is useful for small areas. However, it can get expensive for a larger garden since each bag only covers a few square feet (buying it in bulk from a local garden supply store can save a bit of cash if you have an especially large project). Although the wood breaks down in time, chips, nuggets and bark take months or years to decompose, which limits any benefit to the soil.

Using Cocoa Pods for Mulch

Called cocoa bean mulch, cocoa pod mulch or just cocoa mulch, this product is made of cocoa bean shells that separate from the beans as they are roasted. Since the roasting sterilizes the shells, cocoa mulch is free of weeds and is totally organic, according to Gardening Know How. Many gardeners love the sweet, chocolatey smell of this mulch, and it is also very attractive in the yard.

Cocoa mulch is one of the best mulches for renewing soil nutrition and adding nitrogen, phosphate and potash. It's great for garden beds and veggie patches, holding in soil moisture and limiting weed growth. The key to mulching with cocoa pods is to keep them relatively dry since perpetually wet cocoa shells can develop mold. Dog owners may want to pick a different kind of mulch if there is any chance that the dog will eat the good-smelling shells. Two compounds found in cocoa shell mulch, caffeine and theobromine, can prove toxic to canines.

Using Newspaper for Mulch

What can you do with the daily paper when you finish reading it? You can use it for mulch, and it may be the cheapest vegetable garden mulch around. However, many find that it is not a very attractive look in the landscape. An additional problem is that newspaper mulch can blow away when it's first laid down. Over time, this problem goes away since the paper mats down into a solid layer of paper product.

If those problems don't bother you, give newspaper mulch a try in the veggie garden. If you rip the newspaper into pieces for the mulch, it retains water better than solid sheets, keeping the soil moist. The paper also adds texture and organic content to the soil as it decomposes.

If your main concern is weed control, just layer the newspaper in sheets. The thicker the layer, the better the weed protection. You can also use it as an underlayer for more attractive mulch.

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Using Stones/Pebbles for Mulch

Some mulch materials are inorganic. These types of mulches, including stone or rock mulch, do not decompose, so they do not require regular renewal like organic mulches do. In fact, stone mulch is as close to a one-and-done as you can find, acting a little like hardscaping in the yard. That longevity plus good looks in the garden make this a very popular mulch.

Stone mulch can be made of lava rock, crushed gravel, pea gravel, marble chips or pebbles. As a mulch, stone is durable and easy on which to walk, although in sandy soils, you must install woven ground cloth first to keep the rocks from getting pressed into the sand. Rock mulch will not improve the soil, but it does a good job of controlling weeds. It is best used for walkways and pathways. Rocks and stones reflect heat, which is hard on plants as the weather turns warm and dry in summer, heating plant roots to the point of damaging them.

Using Landscape Fabric for Mulch

It's rare but not unheard of to see landscape fabric used by itself as mulch in a landscape. It is constructed in a solid sheet (e.g., polypropylene) with water drainage holes or is made from woven fibers that allow water to soak through. You purchase it in rolls that are usually a yard wide, with different lengths available. The cost depends on quality, with thicker fabric costing more, and you'll want to factor in the pins required to hold the fabric in place.

Landscape fabric is favored by gardeners and homeowners who are sick and tired of having to deal with weeds. It also helps to keep moisture in the soil. Many gardeners who use fabric as a mulch layer cover it with a more attractive type of mulch, like wood chips or gravel. Placing organic matter on top of landscape fabric isn't helpful to the soil since the nutrients from the decomposing material will not be able to get through to the soil below.

Using Rubber Mulch in the Garden

Rubber mulch is usually made from recycled tires, and that seems like a win-win situation given the hundreds of millions of tires that get tossed every year. However, there are both pros and cons to using this inorganic mulch.

Like other inorganic types of mulch, rubber mulch is very resilient and lasts for 10 years or more. A thick layer will prevent most weed growth in the landscape. Some rubber mulch prevents airborne seeds from landing and germinating, but it doesn't stop weed seeds that are already in the ground from sprouting. You may want to use a landscape fabric first if weed prevention is your number one priority.

Rubber won't improve the soil texture or add nutrients when it ultimately breaks down, and there is some evidence that the decomposition of certain types of rubber mulch can cause byproducts that damage plants. It is also flammable, and if it is ignited, it burns hotter and faster than wood mulch, according to Total Landscape Care. It is most often used for walkways, ground cover and playgrounds.

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From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.

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