If you’re new to gardening or landscaping you may be tempted to omit a mulch layer, but the longer you grow plants outdoors the more obvious the benefits of mulch become. Whether your aim is to make your growing area prettier, healthier, or lower maintenance, mulch is the solution.
The enormous variety of types of mulch can make the process of choosing a mulch for your garden a challenge. Read on for a comprehensive guide to fifteen varieties of mulch.
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Organic Mulch vs Inorganic Mulch
It will be easier to decide on a type of mulch if you identify your priorities and reasons for mulching.
Most people use mulch in their gardens and landscapes for at least one of the following reasons:
- Mulch can create a backdrop for your plants with more visual appeal than bare soil.
- Mulch can suppress weeds, keeping maintenance weeding to a minimum.
- Mulch can improve your plants’ growth by trapping warmth and moisture.
- Mulch can, by decomposing, fertilize your soil and improve its texture and structure .
If you are focused on the first three reasons, you can use either organic or inorganic mulch. However, if you want to build healthy soil for your plants, your best bet is organic mulch.
In this context “organic” doesn’t mean a government certification that the mulch is free of certain chemicals (like “organic” carrots or chicken), it means something more fundamental.
Note: Organic mulches are made from carbon-based life forms while inorganic counterparts uses either rocks or plastics.
Organic mulch is made from materials that are organic, meaning that they were once carbon-based life forms. For example, wood chips are made from trees, and manure is made of plants digested by animals, so both are organic.
On the other hand, inorganic mulch is made from inorganic (non-living) materials. That means it consists of minerals rather than plants or animals. For example, inorganic mulches might be made of rocks or plastics.
The difference matters. As organic mulch decomposes it improves your soil’s fertility, aeration, drainage, microbial life, worm and insect life, etc. Inorganic mulch doesn’t decompose, or at least it does so extremely slowly.
Warning: When inorganic mulches made from plastic or rubber do decompose, they may release harmful chemicals into your soil.
Regardless of what type or types of mulch you use, it is crucial to properly prepare the area and apply the mulch correctly. This step-by-step guide will make sure you get it right from the start.
good for soil
easy to apply
|Should be aged before using
can burn plant stems if placed too close
|Gorilla Hair||Ideal for slopes
good for soil
expensive compared to most organic mulches
|Wood Chips||Cheap or free
easy to apply
good for soil
|Breaks down faster than bark
should be be aged before using
|Straw/Grass Clippings/Weeds||Inexpensive or free
easy to apply
great for the soil
|Decompose quickly so must be reapplied regularly
less attractive to some people
|Compost||Ideal for the soil, you can make it for free||Sometimes difficult to find or expensive
poorly made compost can be weedy
requires regular application
|Cocoa Bean Hulls||Visually attractive
easy to handle
good for the soil
|Expensive and decompose quickly
hazardous to animals
messy application process
|Shredded Leaves||Free and readily available
good for the soil
most available in fall rather than spring
|Newspaper/Cardboard||Often free or inexpensive
layers well with other organic mulches
great for suppressing weeds
|Not attractive without top-dressing
cardboard must be weighed down
pleasant to walk on
easy to maintain
|Spreads to unintended areas
heavy and difficult to transport and apply, expensive to install
requires underlayer and edging
|River Rock||Lasts forever
easy to maintain
extremely heavy and difficult to transport
|Chipped Rock||Long lasting
easy to maintain
heavy and difficult to transport
requires under-layer and edging
|Lava Rock||Lightweight compared to other rock mulches
some find it unattractive
|Black Plastic Sheeting||Cheap
excellent weed suppressant
|Kills the soil along with weeds
requires soaker hoses
requires weighing down
|Landscape Fabric||Great weed suppressant
|Unattractive unless covered
cheap options degrade quickly
|Rubber Chips||Useful for playgrounds||Leaches chemicals into the soil as it degrades|
|Attractive||Should be aged before using|
|Moderately priced||Can burn plant stems if placed too close|
|Good for the soil|
|Easy to apply|
Bark mulch is shredded bark material from softwoods, typically the waste product from a lumber-mill or similar business. It can last as long as 7-10 years before you will need to reapply it.
Note: Bark mulch is a great choice in perennial flower beds, because it protects the soil and as it breaks down it feeds the soil. However, you should avoid putting this type of mulch directly against the stems of tender plants.
Bark is very absorbent, and allows free-flow of air and water into the soil. Pine bark is a bit more acidic, so you may need to neutralize the soil depending on what plants you’re growing. It also breaks down more quickly than other barks. Hemlock bark tends to be a bit pricier, but has a beautiful reddish tone. Cedar bark is preferred for its insect repellent qualities. Some people prefer to blend multiple types.
Wood and bark compost and feed the soil, eventually. However, in the first year or so after it is cut up, bark and wood mulches require nitrogen to decompose. That means layering fresh bark over your garden soil will actually steal nitrogen from the soil.
You can counteract this nitrogen draining effect of fresh wood by adding a nitrogen fertilizer (or a nitrogen-rich substance like fresh grass clippings), but the best solution is to make sure you only use wood-product mulches that have been aged. Ideally wood products should be aged a year or two before you add them to your garden.
Gorilla Hair Mulch
|Ideal for slopes||Flammable|
|Decomposes slowly||Expensive compared to most organic mulches|
|Good for plants|
Gorilla hair mulch is finely shredded cedar or redwood bark so that it has a light, fur-like texture. The natural color is a light reddish brown, but it is also available in a dyed black. It is attractive, and even deters some insects and rodents.
Note: Unlike chunkier bark or wood chip mulches, gorilla hair forms a dense mat, which is great at retaining soil moisture. However, if applied too densely it can create a water barrier instead.
Another benefit of this texture is that it holds together well on sloped beds, so that you don’t end up with a pile of bark at the bottom of the incline.
This mulch is highly flammable and should not be used in areas where cigarettes might be dropped or where wildfires occur.
For more information about using gorilla hair mulch effectively in your home, check out this guide.
|Cheap or free||Breaks down faster than bark|
|Reasonably attractive||Should be aged before using|
|Breaks down faster than bark|
Wood chips are a waste product from lumber-mills, furniture companies, and even municipalities that chip trees that fall on public land.
Wood chips are a popular type of mulch because they can be obtained inexpensively or even for free. You can make your own at home, or get them for free from many municipalities. If you do purchase them at a store, they are available in a variety of colors based on wood type and sometimes dye.
Wood chips are good for weed suppression, but they have a variety of downsides.
Note: Wood chip mulches break down faster than bark, so they may have to be reapplied every few years, depending on the thickness.
Some people try to get around this by applying wood chip mulch too thickly. This is a bad idea and can create problems with mold, rot, and bad odors.
Wood chips do contribute to good soil health, helping the soil retain moisture and attracting worms and beneficial microorganisms, and then decomposing to become well-structured soil over time.
However, wood chips must be aged for at least a year before adding them to your garden or they will leach nitrogen from the soil as they decompose, which can harm your soil unless you add a nitrogen fertilizer.
In landscapes, wood chips work best around deep rooted plants like trees and bushes, rather than annuals. They work particularly well in pathways, under playgrounds, and other places without plants. As with bark, don’t allow wood chips to touch the stems of tender plants.
|Inexpensive or free||Quickly decomposes|
|Easy to apply||Regular reapplication is necessary|
|Great for the soil||Less attractive to some people|
Straw and grass clippings, unlike hay, make great mulch. What’s the difference? Hay is full of seeds, and will fill your garden with weeds. Straw is generally seedless and makes great mulch, as long as it hasn’t been chemically treated. Grass clippings are basically straw you grow yourself.
Grass clippings are rich in nitrogen. So, if you use them fresh, it’s like mulching and fertilizing in one organic step.
Just sprinkle a fine layer of clippings after you mow. As they decompose, they will become nitrogen-rich compost in the soil, making your plants grow even better.
You don’t need to worry about small weeds in your grass-clipping mulch. As long as they haven’t gone to seed they’ll be fine.
Warning: Weeds that have gone to seed (or weeds with rhizomes that have been pulled up rather than trimmed with a mower) must be composted in a hot compost pile before they’re safe to use in the garden.
If you use straw, you can mulch once a year. If there is still straw that hasn’t decomposed the next spring, just rake away the excess and add it to your compost pile. Then, plant your plants and re-mulch with fresh straw. Multiple thin layers are better than a single thick layer when you mulch with grass clippings.
|Ideal for the soil||Sometimes difficult to find or expensive|
|You can make it for free||Poorly made compost can be weedy|
|Requires regular application|
Compost (well decomposed organic matter) makes an ideal mulch. This can be confusing, because to the untrained eye compost might look a lot like your basic garden soil. It may not make a major visual difference, but mulching with compost is one of the best things you can do for your garden.
Compost is finer in texture than any other mulch option, so it should be no surprise that it decomposes and erodes more quickly than the others.
Note: Twice a year is a frequent rate for application of a compost mulch. However, it does have a better weed suppressing effect than you would expect based on its texture.
Compost can be made of plant matter, animal waste, or a combination. Horse, chicken, cow, and bat guano are great choices. However, animal waste must be composted to age it before using it, usually requiring at least a year to cure. Otherwise, animal waste manure may be too high in nitrogen, unbalancing your soil and burning sensitive plants, and it may contain viable weed seeds.
Warning: If you are going to use manure, avoid human, dog, cat, or pig waste, as they can carry pathogens.
Plant based compost (such as composted yard waste) is ideal, but it must be created carefully. Specifically, it needs to be hot compost, having heated to a sufficient temperature to kill weed seeds.
The same is true for horse and cow manure, which can contain viable seeds prior to composting. For more information about this process, check out this guide to hot composting.
Cocoa Bean Hulls
|Pleasant scent||Quickly decomposes|
|Easy to handle||Hazardous to animals|
|Good for the soil||Messy application process|
Cocoa hull chips are unconventional mulch, but their rich color and chocolaty smell explain why this mulch option is catching on. In addition to being aesthetically pleasing, cocoa bean hulls are good for the soil and they deter slugs and snails. Potted plants are a common application for this type of mulch.
Warning: Cocoa hulls’ pleasant smell makes them attractive and dangerous (potentially fatal) to pets and wildlife, so they should only be used judiciously.
Cocoa shells are expensive upfront but they are long-lasting. They should smell intensely of chocolate when you buy and apply them, but the aroma will fade after a few weeks. If they smell musty or the bag is heavy and wet, don’t buy them.
You will want to wear gloves and clothing you don’t mind staining when you spread your cocoa hull mulch. Be careful not to get dust everywhere. After you’ve spread the hulls, water them to help them integrate into a layer.
Shredded Leaf Mulch
|Readily available||Most available in fall rather than spring|
|Good for the soil|
Any time you walk through a natural wooded area, you are walking on soil that consists of biodegraded leaves, forming a natural compost. You can use leaves the same way.
If you have trees of your own, or neighbors willing to save their leaves for you, this is a free option that requires some effort on your part but is great for your garden.
Note: Molding leaves add nutrients, suppress weeds, maintain soil moisture, reduce swings in soil temperature, reduce erosion, and improve soil drainage.
In your landscape or garden, it is best to use shredded leaves rather than whole leaves. Whole leaves can become matted together, reducing the rate of air and water exchange with the soil. You can easily shred your leaves by running over them with a lawnmower. This process also makes the leaf mulch more attractive.
You can use shredded leaf mulch on top of the cardboard. You can also mix it with any other organic compost.
|Often free or inexpensive||Not attractive without top-dressing|
|Layers well with other organic mulches||Cardboard must be weighed down|
|Great for suppressing weeds|
Newspaper and cardboard are used differently, but both can be great mulch as long as you follow a few guidelines.
Standard newsprint and the dyes used on typical brown or white cardboard boxes are plant-based and fine for your garden. However, make sure to remove any tape, staples, or other additional substances and stick with basic newspaper and cardboard.
Warning: Do not use any glossy, colorful, coated papers or cardboards, as these additives and dyes can be harmful.
Here’s how you should use newspapers:
- Begin by shredding your newspaper.
- Then you can use it in one of two ways
- Either use it like straw mulch, in thin layers.
- Or, add it to your compost bin or pile, to bulk up your compost.
- Then use the finished compost as mulch.
Cardboard is an amazing product to use for gardens and landscapes. Cardboard covered with another type of mulch is one of the most powerful weed-suppressing mulch combinations.
Here’s how to use cardboard as mulch:
- Use it whole, like you would use landscape fabric.
- Overlap the edges of the pieces of cardboard so there are no gaps, other than for your desired plants to grow through (cut holes for them as needed).
- Then, cover the cardboard with a thin layer of another type of organic mulch (such as compost, straw, or wood chips).
Once it is soaked with water (whether by irrigation or rain), cardboard will mold to the form of the landscape better. It allows water and air to pass through into the soil. Eventually it decomposes and becomes compost. Cardboard is an integral aspect of many no-till gardens and layered gardens.
|Long-lasting||Spreads to unintended areas|
|Attractive||Heavy and difficult to transport and apply|
|Pleasant to walk on||Expensive to install|
|Easy to maintain||Requires underlayer and edging|
Pea gravel is commonly used for driveways, paths, filling spaces between pavers, etc. However, it also works as mulch in potted plants, and even in some perennial landscapes as a decorative top layer. It helps retain some moisture in the soil.
Note: Light colored pea gravel will tend to have a reflective effect, whereas darker pea gravel will absorb the sun’s heat and warm the soil.
Pea gravel is made of small, multi-colored pebbles, typically about the size of a pea (a quarter-inch, give or take an eighth). The pebbles are smooth surfaced bits of river-rock that are nicer for foot traffic than most types of mulch. Some varieties can be sharper and less suitable for bare feet.
Pea gravel tends to migrate from where you put it to nearby areas of grass or other surfaces. That means that you should definitely use a hard edging material (such as bricks, pavers, plastic or metal edging, or bender board) to create a border.
This will keep it in place as much as possible, both so that you don’t end up with a lawn full of gravel and so that you don’t have to replace the gravel when it thins out to expose the soil.
Note: Pea gravel does have a weed-suppressing quality, but only if you start with a weed-free area and/or underlay it with landscaping fabric.
In your landscaping, you typically use landscape fabric under the pea gravel both as a weed barrier and to make sure the gravel doesn’t mix in with the soil beneath.
If you are using pea gravel for pathways, especially those you’d like to push a wheelbarrow over or put garden furniture on, you need to put a base layer of larger rocks under the pea gravel, to stabilize it.
|Attractive||Extremely heavy and difficult to transports|
Like pea gravel, river rock is a natural form of mulch, even though it is inorganic (never alive). River rock is essentially large pea gravel but it doesn’t scatter away from where you lay it, so you won’t have to top-dress it periodically to maintain the right depth.
Note: River rock absorbs heat during the day and releases it at night, which can improve plant growth but also necessitates more frequent watering.
River rock is several times more expensive than organic mulch. Delivery can also be expensive because it is so heavy. However, it does not biodegrade, so it will essentially last forever.
River rock has a weed-suppressing effect, but like pea gravel it works much better if you start with a weed-free area, because weeds can grow up between the rocks.
The best way to avoid this is to underlay the rocks with landscape fabric. This extra layer also prevents the rocks from sinking and the soil underneath from migrating upward, keeping a more attractive appearance.
River rock does require occasional maintenance. You’ll need to remove fallen leaves, silt, and other debris that get mixed in with the river rock, and wash it.
|Attractive||Heavy and difficult to transport|
|Easy to maintain||Requires under-layer and edging|
Chipped rock is made of moderately small pieces, a size compromise between pea gravel and river rock. It is made of rough chips broken off of larger rocks. Unlike pea gravel and river rock, it is often a single color (white or grey, usually), which can make a very attractive backdrop for your garden plants.
Note: Like pea gravel, it needs to be lined with a layer of landscape fabric, and it tends to migrate so it needs to be held in place with some form of hard edging material.
The rocks have a rough texture, so they are not pleasant to walk or stand on, but they are sometimes used for pathways or driveways. Chipped rock also works well in potted plants.
Chipped rock can serve as an inorganic mulch in the landscape, with a few caveats.
|Lightweight compared to other rock mulches||Requires under-layer|
|Long-lasting||Some find it unattractive|
Lava rock, which comes in red and black, is a popular choice for desert landscapes and playgrounds, but has a variety of potential applications in the home garden. Pumice stone is another type of volcanic rock, and is typically a light grey.
Note: Unlike other rock-based mulches, lava rock and pumice are lightweight and full of air pockets.
Lava rock and pumice have a similar effect to most dark stone mulches. They help the soil retain moisture. They also absorb some heat during the day and release it at night, but less so than solid rocks.
Lava Rock shares many downsides with pea gravel. It needs an underlayer to be an effective weed barrier and edging material to keep it in place. It also requires maintenance to keep it free of debris.
For more ideas about how to use lava rocks in your backyard, check out this article.
Black Plastic Sheeting
|Cheap||Kills the soil along the weeds|
|Excellent weed suppressant||Requires soaker hoses|
|Requires weighing down|
Black plastic tarps were once believed by some people to be an effective type of mulch – after all, black plastic has good weed-suppressing qualities.
Some farms do use black plastic sheets to mulch heat-loving plants whose roots won’t be bothered by the increase in soil temperature. For example, some people lay black plastic and punch holes in it for their tomato and pepper plants to grow through.
Warning: Black plastic sheeting doesn’t just kill weeds. It also blocks air, water, and nutrients from penetrating the soil, killing worms, beneficial soil microbes, and, ultimately, the soil itself.
However, black plastic is not water permeable, and not enough rainwater or sprinkler water will enter the hole for each plant. That means it is essential to lay soaker hoses in place before mulching with the plastic sheets. The area should also be thoroughly weeded at this stage, before laying the plastic.
Also, it does not stay in place on its own. You will need to weigh it down with rocks or boards along the edges, or cover it with a thin layer of another type of mulch. Most importantly, it may leach unwanted chemicals into your soil as it slowly degrades.
Black plastic is a good choice for a temporary mulch, if you want to kill off weeds before planting. However, for most gardeners, it is not a good mulch choice for leaving in place.
Weed Barrier Landscape Fabrics
|Great weed suppressant||Unattractive unless covered|
|Permeable||Cheap options degrade quickly|
Weed barrier geotextiles, popularized in the 1980s, are permeable fabrics used to create weed barriers in landscapes. They may feel woven, like burlap, or perforated with little holes.
In either case, the fabric is designed to allow water, air, and nutrients to soak through it into the soil below, while denying weed seeds below the fabric the sunlight required for germination.
Note: As with black plastic, it is important to weed the area thoroughly before laying the weed barrier, and to keep the areas around the edges of the weed barrier weeded.
The geotextile material is biodegradable, but only slowly. It is especially durable when topped with another form of organic or inorganic mulch (such as wood chips or pea gravel). Adding a layer of another type of mulch on top is also a good idea for aesthetic reasons.
|Useful for playgrounds||Leaches chemicals into the soil as it degrades|
Rubber mulch is made of small pieces of rubber (usually from old tires), around the same size as bark mulch. They biodegrade (slowly) your soil may begin to resemble a landfill’s soil. They are also somewhat flammable.
Warning: If they are not chopped small enough, so they catch and hold water, tire pieces can become a breeding ground for mosquitoes.
This type of mulch should not be used in your garden or landscape but is used sometimes in areas like playgrounds where you need a soft surface and no plants will be grown in the area. However, if you use it for this purpose, make sure your supplier only uses tires without studs or other metal pieces.
Mulch For Every Garden
No matter what your growing situation is, the range of organic and inorganic mulches available means there is an option that will be perfect for your yard. Remember, find a type of organic mulch that works for you, and it will pay dividends for years in the form of enriched soil!