The Ultimate Guide to Mulch



Table of Contents

What is Mulch? Pros and Cons of Mulch
Organic VS Synthetic Mulch Potential Jobs for Excluded Nurses
General Mulching Tips Seasonal Mulching
Other Uses for Mulching Materials Resources


What is the OIG Exclusion List?

Generally speaking, mulch is anything that is spread around or over soil as cover. It has become an important part of gardening and landscaping. Through the years, however, mulch has been redefined to include the surfacing of playgrounds, parks, and horse arenas.

It's become a multi-purpose material used to enhance soil properties for growing plants, to beautifying landscapes, through to cushioning potential falls in playgrounds, recreational parks, and horse arenas.

It's become such a big business that the use of mulch is not without its share of controversies, which we will get to a little further down in this eBook. At this point, a closer look at the different types of mulches and their uses can tell us more about their origins and uses.

*Please note that links to resources further explaining certain terms and concepts can be found throughout the text.

A. Types of Mulches

Certain kinds of mulches have been around since gardening became a widespread practice. Of course, organic mulches have existed longer than their synthetic counterparts, since the former can be easily sourced from nature.

Organic mulches decay and decompose over time. They are made from natural or biodegradable materials. Synthetic mulches either do not decompose or else do so very slowly, and are usually the products of industrial recycling and manufacturing.


Wood is a popular mulch option. It typically comes in the form of chips, either as coarse byproducts of tree pruning, or as more uniformly processed byproducts of untreated timber.

Grass clippings are collected and used as mulch after a lawn is mowed or trimmed. They are usually mixed with other composting materials like fallen leaves and soil.

Leaves are raked and then spread over garden soil to act as mulch. Because they are light enough to get blown by the wind, they are often shredded into more manageable pieces.

Straw is collected into hay bales and spread onto the ground as winter covering for gardens.

Rock mulches can come from pebbles, river stones, and gravel. The variety of sizes, colors, and textures of this material allow for many gardening and landscaping possibilities.

Paper and cardboard are common recyclable mulching materials. They can be soaked in water to increase their weight, and then applied as the base layer for heavier mulching materials.

Bark is a practical organic mulching option since it's readily available in landscapes and gardens with trees. They are typically used in layers.

Other common organic mulches include peat moss, sawdust, and pine needles.




Plastic mulch is used to suppress weeds in gardens and landscaping. It also helps regulate irrigation for large-scale vegetable gardens. Currently, biodegradable or compostable plastic mulches are being created to respond to environmental issues and awareness, and in accordance with ASTM standards.

Recycled rubber is fast gaining popularity as an alternative sustainable mulching material. It is made from either shredded old tires or sneaker soles.

Landscape fabrics or plastics are also known as "weed cloth" that are spread over garden soil and pinned down. They are designed to work with organic materials and can last for a decade.


B. Popular Uses for Mulch

As diverse as mulching materials are, so have their uses become. Over time, mulch has evolved from just being garden material to becoming playground surfacing, horse arena infill, and even military training surfaces.

Gardening Garden mulch, whether it is natural or synthetic, is used to improve moisture retention in soil so that plants can benefit from it. It's also designed to reduce or prevent weed growth altogether. Mulch is also an effective soil insulator.
Playground/Athletic Arenas Safety is a top concern in playground surfacing, and mulch can efficiently address this. Different kinds of mulches offer different levels of fall-from-a-height shock absorption and protection. As for athletic tracks, rubber mulch also offers the kind of resiliency that can improve a runner's performance while protecting feet and legs from hard impact.
Landscaping In landscaping, mulches are used to add visual impact and decorative appeal to homes, businesses, and public places. The many textures, shapes, and colors of mulch make this possible.
Horse Arena One of the surprising new uses for mulch is as equestrian infill. Shock absorption and better performance are the main reasons for its use as horse arena surfacing. Rubber mulch in particular offers these benefits.


Pros and Cons of Mulch

For all its benefits, mulch also offers some drawbacks. This is true for both organic and synthetic mulch, so it is up to you to weigh their pros and cons and consider your needs before deciding which one to invest in.

A. Benefits

Ordinary mulch users and experts alike have weighed in on the various benefits mulching offers. Here are some pros based on its more popular uses.

For Gardening and Landscaping

Mulch is used to prevent weeds from germinating and spreading all over your garden. It also helps retain soil moisture so your plants' roots will not dry out during hot months. In colder seasons, mulch also protects plants from getting frozen.

The great thing about organic mulches like leaves, bark, and grass clippings is that they are available any time and everywhere, so they can be had for free. Gravel, peat moss, and stone can be either freely sourced or bought, but they are easy to apply and still look natural.

Soil erosion is something landscape fabric can solve, because it prevents hillside garden and landscape soil from sliding downwards. And because pets cannot dig into soil covered by weed cloth, young plants have a better chance to thrive.

Organic mulches also offer added nutrients to your soil and plants when they decompose. Synthetic mulches like shredded rubber and landscape fabric, on the other hand, make sure fertilizer and water go straight to the plant roots since they don't retain moisture. As an added bonus, the weight of rubber mulch nuggets makes them stay in place even in rainy and windy weather.

For Playgrounds One of the biggest advantage of mulch for playgrounds and athletic tracks is shock-absorption. Different kinds of mulch offer various degrees of cushioning especially for hard-impact activities like running and jumping.
For Horse Arenas Additional coverage on top of horse arena surfacing provide a degree of protection for horses' hooves and their riders' backs. As with playgrounds, different kinds of mulching offer a variety of protection. Rubber mulch so far has the highest level of shock absorption to offer for both the horses’ legs and possible falls for their riders. This makes it an ideal mulch for equestrian dressage, training, and races. Also, since rubber discourages the growth of weeds and the presence of moisture, the chances of fungal infection and slipping on the arena become significantly less.

B. Drawbacks

Mulches also have certain disadvantages, as illustrated by their common uses below.

For Gardening and Landscaping

Not all mulches perform the same way. Some organic mulches like grass clippings and leaves decay quickly, and can go to seed and germinate in garden beds. Some, like bark or wood chips, can be too acidic for your plants to handle.  

Straw and hay can attract rodents, and wood chips and bark could prove inviting to insects, particularly termites. Care must be taken during hot months because certain mulches like dried leaves, hay, straw, and wood chips could catch fire easily.

Landscape fabric prevent plants from intermingling because it provides a barrier for re-seeding flowers and fruit to take hold in the soil.

As for rubber mulch, complaints about its industrial smell and possible chemical leaching in soil have been brought up time and again.
For Playgrounds As far as shock absorption from falls go, rubber mulch offers the highest level of protection for playground-related impacts. Organic mulches like sand, wood chips, pebbles, and others do not offer much by way of protection and resiliency. However, there have been numerous concerns about how rubber mulch gets hot in prolonged exposure under the sun, and its accompanying smell and possible toxicity.
For Horse Arenas Clay arenas have benefited from the use of rubber mulch surfacing, but fears of rubber mulch ingestion have been raised. Other organic mulches in turn cannot offer much protection for slipping or sliding, and possible injuries from high-impact equestrian training.  



Organic VS Synthetic

If you're in the market for mulching material, whether it's for your garden, landscaping needs, or for something bigger like a playground or athletic arena, you will have to weigh the relative merits of organic and synthetic mulches available. Below are some of the most common arguments for and against both organic and synthetic mulches.

A. Why get organic mulch?

  • It is cheaper or can be had for free.
    Fallen leaves, straw, rocks, grass clippings, bark, and many organic mulching materials typically cost less than synthetic mulches. If you're resourceful, you can have them for free by collecting them yourself or gathering them where they're plentiful.
  • It contributes nutrients to soil.
    Because it decomposes, organic mulch passes nutrients to the soil and plants as it rots (which synthetic mulches can't do).
  • There are more organic options.
    You won't have to go to a store to select what you need. You can simply mulch with what you have or what's readily available, thanks to natural resources: trees, grass, rocks, sand, etc. around you.
  • It is all-natural.
    Your garden will look, feel, smell, and be as nature intended it to be.

B. Why get synthetic mulch?

  • It is cheaper in the long run.
    Because you won't have to spend too much on top-ups, replacement, or additional gardening peripherals like pest control and fertilizer, synthetic mulch ends up costing you less over the years. This is true of landscape fabrics and rubber mulch, which can last ten years without replacement.
  • It offers better shock-absorption.
    Rubber mulch provides a softer alternative to traditional mulches which don't offer much by way of protecting from falls. With proper installation and adequate depth (around six inches), a rubber mulch surface will give up to 16 feet of critical fall height protection compared to gravel or wood mulch. Even the playground at the White House uses rubber mulch.
  • It requires less maintenance.
    Rubber mulch and landscape fabric stay put because it won't float away in rainwater, freeze in winter, or get blown by the wind. A bit of raking now and then is all you need to do.
  • It recycles unwanted landfill material.
  • Tons of old tires have become a landfill problem, which is why recycling them into rubber mulch became a viable solution. Due to the process of recycling and repurposing rubber mulch undergoes, some states like Kentucky have incentivized its use.
  • It is EPA-endorsed. The Environmental Protection Agency (EPA) has actually endorsed the use of rubber mulch for playground surfaces. The agency has also done surface and atmospheric tests on playgrounds using rubber mulch, and found no significant adverse human or environmental effects.

To gauge the performance of rubber mulch against popular organic materials like rocks, pea gravel and wood chips, here are comparison charts that list their relative merits.

Rubber Mulch vs Pea Gravel

Benefits Rubber Mulch Pea Gravel
Protection from falls At just 6 inches in depth can provide protection from falls from over 12 feet. Unlike pea gravel, temperature does not affect rubber mulch and performs just as well in cold weather as is does in warm climates. At depths of 9 inches or more can sufficiently reduce the impact of a fall. Can become quite hard in cold weather which can affect impact.
Maintenance Doesn't break down and doesn't compact. No need for annual replacement. General inspection of the surface, raking the material to ensure it stays at a consistent depth, and periodic top up every few years Will begin to break down into smaller particles over time. Can cause "hard pans" made of dust from broken-down gravel, which is difficult to break apart and can be dangerous. Requires annual replacement.
Visual appeal Available in a host of both earth tones and bright, vibrant color options for playgrounds, gardens, and athletic or horse infills. Provides a natural, organic type of appearance. The material is usually grey in color but depending on the source of the stone, some color variations may be available.
Price tag Comes with a higher initial purchase price but can often be offset over time due to reduced maintenance and top up requirements. Falls into the lower cost category with pea gravel being the lowest cost option. Requires annual top up.

Rubber Mulch vs Rocks

Benefits Rubber Mulch Rocks
Nutrition Doesn't absorb water or fertilizer so all soil and plant needs goes right into them. Doesn't decompose so offers no nutritional benefits to soil and plants in a garden. Insulate cold-sensitive plants with warmth and help them thrive even in harsh conditions. While organic, also do not offer nutrients that enrich soil and plants.
Lifespan Offers a longer shelf life because of sufficient weight that doesn't float away or get blown by breeze. Can be used for mulching and landscaping purposes for over a decade without degrading. Sufficiently heavy so can stay put for longer period compared to other lightweight mulches.
Durability Is the result of recycling tires, therefore made to withstand harsh weather conditions, making it ideal for low maintenance mulching purposes. Typically comes from hardy volcanic deposits. Can withstand high winds and harsh weather conditions
Price tag Initially has a bigger price tag per sq.ft. but requires less top ups and replacement in the long run. Can be sourced anywhere at any time. Can stay in place far longer than other organic mulches, so requires less top ups and replacement.

Rubber Mulch vs Wood Chips

Benefits Rubber Mulch Wood Chips
Weed/mold control Can help dehydrate unwanted seeds and protect the plants in your garden. Lets water pass straight to soil so lesser chance of mold and fungi. Because of decomposition, could create a more favorable environment for weeds to thrive, and mold/fungi to grow.
Nutrition Merely provides a layer or cover for your garden and does not enrich it with nutrients. Chemicals such as zinc from the rubber might find their way into the soil and affect soil and plant quality. When treated or colored with chemicals, could prove harmful to both soil and plant life. Nutrients in organic, untreated wood chips can serve as fertilizer and integrate into the topsoil, thus encouraging biodiversity.
Protection from pests Doesn't rot so pests are not attracted to it, will not build a home in it or make it their primary food source. Attracts termites and other insects that can ruin not just your garden, but also wooden parts of your home.
Attractiveness Comes in a wide variety of colors. Tends to hold its color much longer, and as long as 10 years. Has the natural look, feel and smell of real organic materials. Can be treated or colored to enhance landscaping.

Price tag

Initially will cost more than wood chips but significantly reduces maintenance and replenishment costs. Initially cheaper, though wood chips might need to be replaced every two years because they decompose. Cost of termite control, top ups, or replacement can add to expense.



Common and Specific Mulch Problems

Mulch ado about nothing? Perhaps no other consumer product has polarized the mulching community as much. Aside from the natural vs synthetic mulch debate, the advantages and disadvantages of each type of mulch also affect gardening, landscaping, and infill decisions.

Gardeners, landscape professionals, and those who regularly use mulches recognize that no two mulching materials (whether manmade or from nature) are created alike. What may generally work for one garden or playground may not work for another.

Other factors like soil quality and the weather should also be considered. This chapter looks at both the common complaints and the specific problems of different kinds of organic and synthetic mulches.

A. General complaints about organic mulch

  • Molds.
    Certain natural mulches like shredded coconut shells attract molds when they get wet or as they age. Slime molds in particular produce small spores that dry up and spread around quickly.
  • Sour smell.
    The decaying process brings about an unpleasant odor in your garden or playground - not a good olfactory experience in designated rest and recreational zones.
  • Artillery fungus.
    Aptly named for its ability to shoot microscopic spores as high as the second story of a house, artillery fungus is difficult to remove and stubbornly sticks to any surface it lands on. It thrives on decomposing matter.
  • Constant maintenance.
    Decomposing mulches need to be replaced regularly to discourage fungal and weed growth (and general mess). Lightweight ones that get displaced by wind or water need annual topping up or replacement.  
  • Attractive to rodents and insects.
    Wood, shredded husk, straw, and other natural materials which rodents and insects (especially termites) can get their food or shelter from will attract them on a regular basis. This is especially problematic if you have fruit-bearing plants, outdoor structures and furniture made of wood, and grain/seed storage.
  • Insufficient shock absorption.
    In playgrounds and athletic arenas, organic mulch surfaces don’t offer the kind of springiness rubber mulch does and therefore do not absorb shock as efficiently. Others, like straw and grass clippings, can become slippery when wet and even add to the likelihood of falls.

B. Specific problems of different types of organic mulches

Type of organic mulch

Specific problem

Wood chips

High in carbon, therefore could cause nitrogen deficiency among plants

Grass clippings

Quick to decompose; can become an ideal bed for weeds to germinate


Gets easily blown around by a breeze and sticks together when wet


Flammable and gets blown away in light wind


Weeds can germinate in the spaces between rocks


Highly flammable and can take some time to collect as mulching material


Can turn sour fast during wet seasons


Absorbs water and liquid fertilizer and can also cause nitrogen imbalance in the soil

Coconut husk

Poisonous to pets; can grow molds quickly

C. Common complaints about synthetic mulch

    • Not pet-friendly.
      Consumers have raised concerns about pets swallowing rubber mulch or developing allergic reactions when they come into contact with it. In the case of landscape fabric, sharp claws and fangs can puncture holes in the cloth, which allows gaps for weeds to germinate.
    • Looks fake.
      When inspected closely, rubber mulch, landscape fabric, and plastic turf can look and feel (and smell) too industrial for many people. Rubber mulch usually comes in a variety of colors, though many landscaping and gardening professionals prefer browns and greens that echo the colors of bark, soil, and leaves. Landscape fabric can be combined with or hidden under organic mulches.
    • Can leach chemicals into the soil.
      Clinical research and laboratory studies have detected the presence of zinc, cadmium, and lead in rubber products, which could affect soil and water quality. There is still no conclusive evidence for human toxicity levels, though.
    • Health concerns.
      Consumers worry about sensitivity to rubber and plastic products, irritation of the skin, eye, and mucous membranes, and other adverse effects of synthetic mulch exposure.
    • High price tag.
      Even if its long term benefits outweigh the initial expense, many people find rubber mulch’s price tag too steep (which is around four times higher than wood chips’).

D. Specific problems of different types of synthetic mulches

Type of synthetic mulch

Specific problem


Needs a special irrigation system and fertilizing process because it is non-porous.

Rubber mulch

As with new rubber products, tends to give off an industrial smell when first installed. Doesn’t contribute nutrients to soil and plants.

Landscape fabric

Not ideal for a garden that needs constant re-seeding, as tearing out and re-installing the fabric can be tedious. Will deteriorate over time (in about a decade) but won’t contribute nutrients to soil and plants.


General Mulching Tips

Different mulching materials make for different mulching techniques, but there are general rules to follow if you don’t know where to begin.

A. How much mulch is needed?

First, consider what you will be using the mulch for: a garden, for landscaping, or for playground surfacing? This will help you determine the depth and width of the area that needs mulching. Multiply the length of the area by its width to figure out the square footage. If the area is uneven, you can divide it into smaller rectangles, then add up the total of all the rectangles to arrive at the square footage. Or, you can simply use a square footage calculator to compute for it.

Multiply the square footage by the thickness in inches you want to apply.
Online conversion calculators such as this one can help you convert weight, length, area, and volume so you can come up with the proper measurements for your project. In turn, your mulch supplier can give you a price quote based on your measurements.

B. How to apply mulch?

First, know your purpose for mulching. Are you going to use it primarily for weed control, to cover a pathway, or as infill for a playground or athletic field? Then consider the availability of the mulch in your area. For gardening and landscaping, organic mulches are usually easy to come by, like with leaves, grass clippings, sand, and rocks. If you are using straw for mulching in the winter, layer 4-6 inches to insulate your vegetable garden. Grass clippings can be applied at 3-4 inch layers, but fluff it up when it starts to smell. Fallen leaves have to be shredded so they don’t get blown away; once they’re in the right size, a 2-4 inch layer will suffice for your garden. Rubber mulch still offers the best shock-absorption capacity for playgrounds and athletic fields. Apply at least a six inch layer of rubber mulch and refer to the CPSC playground safety standards for proper application.

C. What to do after applying mulch?

Again, it all depends on the type of mulch and the purpose of mulching. If you’re using organic mulch, you will have to top up, fluff, rake, or replace it altogether in the span of a year. Rubber mulch requires a bit of raking to smoothen but it can last for a decade without needing to be replaced. Mold can grow on coconut husks and shells, so you have to be vigilant about washing them as they can affect your plants’ health. If you’re using straw or hay, make sure they haven’t gone to seed yet so no weeds can germinate on your soil. Grass clippings decompose quickly, so mix some peat moss to slow it down. Sawdust needs constant watering because it absorbs so much moisture. Always be alert for possible fires that can start with flammable mulching material like paper, hay, and rubber.



General Mulching Tips

Whether it’s spring, summer, autumn, or winter, mulching should be part and parcel of your gardening and landscaping activities. Know the best season to schedule your outdoor mulching activities, and learn tips to do them properly.

A. Advantages of seasonal mulching





Keeps soil temperature even so hibernating plants won’t get stressed from weather fluctuations

Retains soil moisture so plants don’t dry out in the heat

Prevents weed germination even when plants are dormant

Protects plant roots from freezing in cold weather

Best season to check for weeds or diseased plants, and to reapply mulch over new saplings and seedlings

Best season for sourcing organic mulches as grass clippings, leaves, straw, pine needles, sand, etc. are in abundance

Best season for weeding and mulching due to weather that isn’t too hot or too cold to be outdoors

Best season to spread a thicker layer of mulch to protect plants and soil from freezing

B. Helpful tips for seasonal mulching





Right time for composting because organic materials are plentiful and the soil can benefit from nutrients.

If you use grass clippings, replenish often. Neglected grass clippings can go to seed quickly so apply only an inch at a time.

Prior to mulching, rake fallen leaves before moisture sets in. It will improve soil quality and turf condition in time for winter.

Avoid using straw or hay in cold season, as rodents and other small animals can make nests out of them.

Plant perennials like roses during spring. They will be in full bloom during warm weather.

Avoid applying mulch too closely to tree bases. The mulch can retain excess moisture and cause rot, or attract insects and rodents.

Consider using black plastic mulch in preparation for your winter vegetable garden because they help warm the soil for vegetables seeking heat.

Consider using rubber mulch for outdoor footpaths because it doesn’t freeze and gets slippery


Other Uses For Mulching Materials

With some imagination and creativity, common mulching materials can go beyond their expected uses.

A. Practical

  • Protect packages using shredded rubber mulch. If you have an abundance of rubber nuggets for your gardening project, you can do away with messy packing peanuts and use those instead. The inherent springiness can protect fragile items in boxes.
  • Use shredded paper as flooring for chicken boxes/coops. It protects newly-laid eggs and is easier to clean out and turn into compost afterwards.

B. Decorative

  • Build an outdoor fire pit using a bag of crushed rocks, sand, and a steel ring to add warmth and charm to your backyard gatherings.
  • Have a patch of soil where nothing seems to grow? Go crazy creating ground mosaics using mulching material of different colors and textures. You can design a “pond” using blue, green, and white mulch, for example.
  • Select pretty fallen leaves before raking and mulching them in autumn. They can be the center of creative fall projects like garlands, greeting cards, and centerpieces.

C. For Curb Appeal

  • Flagstone walkways or paths can add flair to your home. Rubber mulch in particular can add stability to your walking surface because it interlocks like a mat.
  • Build curving landscape borders for exterior panache. Rock, wood, and rubber are great choices for garden and landscape edging because they can keep mulch in place for many year