What is all this talk about mulch mats?

In addition to different materials, mulch can take many different forms. Shredded bark, bark nuggets, rubber, coco, and plastic sheets are just a few forms you may be familiar with. Something that is relatively new to the industry, and seems to be on everyone’s lips for this upcoming season, is the ‘mulch mat’. It has advantages, and disadvantages, that the other types have, but it just may be the form of mulch you’ve been looking for.

What is a mulch mat?

Mulch Mats with weed control

A mulch mat is mulch, but in a roll form. Think of it as a blanket that you lay across the ground and anchor it down. This blanket provides the three main benefits of mulch: it suppresses weeds by blocking out sunlight; it provides erosion control to your soil and its precious nutrients, by retaining moisture rather than having it fall directly on the soil; and it moderates soil temperature, giving your plants the best chance of survival.

There are two main types of mulch mats, similar to the two main types of mulch—organic and inorganic. Inorganic mulches include synthetic weed blocs and plain plastic sheeting. They break down very slowly (or not at all) over time. Organic mulch mats can be made from hemp, flax, or coco fibers, or even paper. They break down with exposure to the elements, and may help enhance the soil as they do so. The time it takes an organic mulch to decompose is dependent on many variables, such as precipitation, organic content of the soil, and foot traffic.

Why mulch mats?

So let’s look at some advantages of mulch mats.  The heavier the mat, the easier it will be to install on windy days.  Have you ever tried laying down sheets of newspaper or plastic in windy conditions?  It can be a frustrating experience.  The natural fiber organic mulch mats have a great heft, and because they are porous, they allow some wind to pass through.  Very strong winds will still move these types of mats as they’re being installed, but a pretty stiff wind can exist and it’s still a simple task to install them.  Once installed, anchor them down, using a stake or pin, stones, or 2x4 wood boards if temporary.

Anchor Stakes

This same theory holds true for installing mulch on a hill.  Loose mulch can be buoyant, and may blow or float down a hillside, depending on conditions.  Plastic sheets would turn a hillside into a water slide in heavy rains.  The ideal mulch on a hill is one where it stays in place in tough environmental conditions, and allows water to slowly seep through it into the soil.  A properly anchored mulch mat does this very well.

Mulch Mats with Anchor Stakes

A mulch mat made from the proper material conforms to the soil shortly after placement.  This intimate contact with the soil keeps soil in place, allows water to infiltrate uniformly, and helps keep the matting on slopes.  It has fantastic “drapability.”  And because mulch mats aren’t made with netting, the possibility of “bridging”, or leaving gaps between the material and the soil, is greatly reduced.  This is critical in erosion control applications.

Mulch matting can be much lighter than other types of mulch.  For example, for a given area, hemp mulch mats weigh just 7% of the equivalent shredded bark mulch.  This assumes a bark mulch depth of three inches.  And this is main reason mulch mats are so much lighter—you just lay one layer over your landscape beds.  With loose types of mulch, there is a recommended depth the mulch should be.  Lighter mulch means less hassle buying from a local store or online, less transportation costs, and greater options in storing leftovers.  If you’ve ever purchased a yard or two of loose mulch, you can relate.  After ordering it, it arrives at your home (typically with a delivery charge), and is dumped in the driveway, taking up valuable space until you use it all.  You may have to carry or wheelbarrow the mulch to your beds to install it.

And you must use it all.  What do you do with any extra?  Or if you didn’t purchase enough?  And here is another advantage of mulch mats: it’s easy to estimate how much you need.  Because the mats are a consistent thickness, you only have to calculate area, not volume, to figure out how much you need.

Natural Mulch mats are designed around two major features: they contain netting, or they don’t.  Mulch mats designed around netting may be stronger than those without.  They may also last longer, because as the main material degrades, the netting (made from a different material), will degrade at a slower rate.  Mats can contain natural netting, such as jute, hemp, or coir, or a synthetic netting.  Synthetic netting may be photodegradable to accelerate its degradation, but must be subjected to sunlight to start the process.

Mulch mats designed without netting are normally manufactured using a needle punch technique.  Fibers are spread out on a moving bed.  Hundreds of barbed needles are then pushed through the fibers at a given rate, entwining the fibers in a random matrix.  This fiber entanglement is what holds the mat together.  The needle design, puncture depth, puncture rate, and how fast the moving bed travels are all variables used to reach the design objective.  Because they contain no netting, these types of mats are used in areas where foot traffic, mowers, or wildlife has a risk of interacting with netting.  Schools, parks, golf courses, and riparian habitat restoration are examples.

Mulch mats are finding a niche among landscapers, maintainers, gardeners, and those who need an easy to install, easy to store solution for mulching and light erosion control.  For most applications, use a natural, net-free mulch mat.  For very steep slopes, areas where biodegradability is not an issue, or if cost is the biggest consideration, synthetic mulch mats are appropriate.