Yard preparation: Diving into the different types of mulch

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Updated Jun 16, 2022

Shutterstock 1156975852Mulches can be a fairly popular addition to a landscape, but when it comes to choosing which type is best suited for your customer, how do you decide?

Regardless of whether the mulch is synthetic or natural, it will perform the same three basic tasks of suppressing weeds, protecting against extreme temperatures and reducing soil water losses.

Find out what you need to know about the many different types of mulch and where they each prove most beneficial.

Decisions, decisions

According to the Cornell Cooperative Extension, along with the three previously mentioned characteristics, a good mulch will also demonstrate a few added qualities.

“The ideal mulch is economical, readily available and easily applied and removed; stays in place well; and supplies organic matter to the soil, yet is free of noxious weeds, insects and diseases,” the Cornell Cooperative Extension says online.

While there is no one size fits all option when it comes to mulch, understanding each type can better help you choose the option that will fit best in your customer’s landscape.

The first choice to make, according to the Cornell Cooperative Extension, is to decide whether your customer’s landscape will need a summer or winter mulch. Based on the current time of the year, a winter mulch would be the preferred option for the time being.

“Winter mulches are used primarily as insulation for woody plants, laid down in late fall to keep the soil evenly cool throughout the winter,” the Cornell Cooperative Extension says online. “Straw, shredded leaves and pine needles are all effective winter mulches. Mulches applied for winter protection should be laid down in late fall, once the soil has cooled but before it has frozen.”

Advantages and disadvantages

According to the Alabama A&M and Auburn Universities Extension, adding in mulch to your customer’s yard can have many benefits, such as the three mentioned previously, as well as preventing rain from compacting the soil’s surface, decreasing soil erosion and overall just making the appearance of your customer’s landscape look more uniform and put together.

For customers wanting to stick with green alternatives, the Alabama A&M and Auburn Universities Extension says that organic mulches can also add certain benefits to the area.

“Organic matter used as a mulch can improve soil structure, drainage and aeration,” the extension says online. “As it decays, the organic mulch material becomes incorporated into the topsoil. Decaying mulch adds nutrients to the soil.”

According to the Cornell Cooperative Extension, organic or mineral mulch needs to thoroughly cover an area to a uniform depth in order for it to be most effective. Bare or low spots will be prone to more problems with weeds, and uneven mulch will not be able to properly insulate the soil.

In areas where grass needs replacing or where it’s hard to maintain and mow, mulch can act as a replacement to groundcovers, and when added around trees and shrubs, mulch can help protect plants from routine landscaping services.

The Alabama A&M and Auburn Universities Extension says that there are, however, a few disadvantages that accompany using mulches.

“The cost of some materials can be a drawback to large-scale mulching,” the Alabama A&M and Auburn Universities Extension says online. “Some mulches are also not readily available. If large quantities are required, buying bulk loads of mulch is less expensive than buying mulch by the bag.”

The Alabama A&M and Auburn Universities Extension also notes that wood chips and sawdust used as mulches will have a high carbon content, which could potentially remove nitrogen from the soil. This, the extension adds, can be fixed by simply adding in extra nitrogen fertilizer.

The extension also adds that heavy mulching over many years can result in a mat of mulch and soil that will cover the crown area of the plants, and it’s always a good idea to avoid piling an excess of mulch at the base of a tree, as this will result in the infamous mulch volcano.

Different types

Wood chips

Wood chips are a very common type of mulch, and they will have a high carbon and nitrogen ratio, which means the decomposition process may temporarily reduce the supply of soil nitrogen fertilizer that gets to the plants.

“Wood chips tend to lose more of their decorative appearance over time, weathering to a gray or silvery gray color,” the Cornell Cooperative Extension says online. “Because of this, people often renew wood chip mulches each year by adding an additional 3 to 4 inches of chips. This over mulching not only wastes mulch but also can suffocate the roots of shallow-rooted species and cause cankers to develop around the bases of susceptible trees and shrubs.”

Instead, the extension recommends renewing the mulch every two to three years, as well as churning up existing mulch before adding a new layer.

Straw and pine needles

Straw is typically widely available and pretty inexpensive, but the Cornell Cooperative Extension says it does have a few potential drawbacks that need to be recognized before it’s used.

Not only is straw highly flammable, but it also contains grain seeds that can germinate, it has the potential to harbor rodents, it must be renewed annually, it can be easily blown away, it’s not quite as aesthetically pleasing as other types of mulch and as it decomposes, it can lower the soil’s nitrogen supply. But straw isn’t all bad.

“It is cheap and effectively suppresses weeds and reduces soil water losses,” the Cornell Cooperative Extension says online. “As a winter mulch, it protects tender roots from cold temperature injury.”

Pine needles, on the other hand, do have a pleasing look to them and they also will acidify the soil when used around acid-loving plants.

Pine needles will also decompose slowly, are fairly easy to work with and are resistant to compaction. If pine needles will be used year-round, they will need to be replaced annually.

Geotextiles

Over the past few years, the Cornell Cooperative Extension says geotextiles have become popular in the world of mulch, as these non-woven and woven fabrics of polyester or polypropylene are said to be an improvement over black plastic.

The Cornell Cooperative Extension says geotextiles allow fertilizer, water and oxygen to easily penetrate through the soil, while also reducing surface evaporation, and they can also help block weed growth.

“Used alone as mulches, geotextiles can be degraded by the ultraviolet rays of the sun,” the Cornell Cooperative Extension says online. “They are used more frequently as mulch underliners, enhancing the weed-suppressing ability of the mulch while separating the mulch and soil.”

The extension notes that non-woven polyester fabrics will typically last longer and have a better resistance to both temperature and chemical degradation, but the polyester mulches are usually more expensive.

“Before a geotextile is applied, the area to be mulched should be cleared of all weeds,” the Cornell Cooperative Extension says online. “Landscapers who have worked with geotextiles have found that application is easiest when shrubs are planted in weed-free soil first; then the fabric is laid on top and slits are cut that just allow the fabric to be worked around the base of each plant.”

The final step of using a geotextile is to apply a 1- to 3-inch layer of mulch over it to help improve appearance, decrease deterioration by the sun and reduce water.

The Cornell Cooperative Extension does add that while geotextiles might be an advancement in the mulch market, they do not prevent all weed growth, especially grass types like nutsedge and Bermuda grass.

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