Do Rocks Make Good Mulch?

You could have seen an growing quantity of rocks used for metropolis landscaping installations and even in your neighbor’s gardens. Rocks have been used as mulch for fairly a while, and the phenomenon shouldn’t be new. 

This would possibly lead folks to marvel if rocks actually do make good mulch. They could marvel in the event that they break down like different pure mulches, offering a small, slow-release of vitamins to the backyard soil. Security for the backyard is a priority if you end up contemplating their use.

The reality about rock mulch lies very a lot within the sorts of rocks which can be used. There are such a lot of differing kinds; some are helpful, whereas others needs to be left for various initiatives. The kind of backyard comes into play as effectively.  

Widespread Rock Makes use of

Rocks are an inorganic materials, versus natural mulches like straw, wooden chips, and leaves. This implies rocks don’t break down over time in any manner that may profit the soil, at the least not instantly. 

Whereas there are geological areas the place rock contents are current within the soil, it takes a very long time for them to decompose naturally. The rocks we’re speaking about are largely nonetheless complete or solely barely decomposed. In that vein, there are a couple of alternative ways to make use of them. 

Pathways and Borders

Close-up of a garden path made of stones and wooden planks. The path is completely strewn with medium-sized river stones of yellowish-brown shades. They are smooth and come in different shapes and sizes. On both sides of the path there are rectangular red-orange bricks in the form of a border.
Improve your backyard with rocks for accents, borders, pathways, and basis safety.

Use rocks so as to add curiosity to the backyard by way of accents, edges, and pathways. A river rock border can present shade to the panorama and act as a channel for water to stream by means of.  

Add some rocks to the realm alongside the inspiration of your home to maintain it away from filth that would harm your house over time. Gravel pathways will be set, and even gravel patios will be set someplace within the panorama to stage the bottom and embody a seating space. 

Architectural Curiosity

View of a small conifer garden with large decorative stones between the plants. The flower bed includes plants such as Blue False Cypress, English Yew, Pinus mugo, Conifer and Pittosporum 'garnettii'.
Massive rocks add dimension and aesthetics, serving as seating or creating topography in landscaping.

Massive rocks are sometimes employed to offer dimension and aesthetic attraction to a rising space. In my time as a landscaper, we regularly used smaller mossy rocks to create a boundary between lawns and driveways and construct up retaining partitions for planting beds. 

Make use of giant rocks to offer seating in a backyard, or allow them to act as an area to construct up the soil for including topography to a flat space or tiers to a slope. You could discover these giant rocks in municipal landscaping, as they’re fairly costly and tough to maneuver round at dwelling. 

Rocks as Mulch

View of the ornamental flowerbed with perennials and stones made of gray granite. The flowerbed is completely mulched with gray-white pebbles. The flower bed grows such plants as Orpine, Black-eyed Susan, Woodland sage, ornamental grass and other national plants.
Xeriscaping led to the widespread use of gravel as a substitute of lawns for water conservation.

With the considerably latest reputation of xeriscaping and its capability to preserve water, folks started to tear out their lawns in favor of gravel. That is most likely the preferred use of rocks as mulch, and that is most certainly the way you’ve seen it within the backyard. 

River or lava rocks are employed equally. In some conditions, they act as the highest layer of a backyard, and their predominant position is to suppress weeds whereas permitting water by means of to the soil layer. Whether or not or not that is the most effective use of rocks as mulch is up for debate, although.

Is Rock Mulch Okay for Gardens?

There are some methods to make use of rocks as mulch which can be truly efficient and helpful to the backyard. There are additionally different methods to make use of rocks that can trigger issues down the road. Let’s begin to deal with this matter by discussing the ups and downs of rock mulch. 


Close-up ornamental flower bed with perennial pine and gray granite boulders and pebbles. The soil is completely mulched with pebbles. Berberis thunbergii Golden Nugget, Cymbopogon citratus and Lavender-cotton grow in the flower bed.
Rock mulch inhibits weed development, aids in straightforward weed detection, gives drainage, and prevents soil erosion.

In case you have issues with annual and perennial weeds, rock mulch can stifle a lot of their development. With rocks, finding rising weeds is less complicated, making mattress upkeep easier. When weeding, a shade distinction between the inexperienced weeds and your rock of alternative helps to simplify the duty. 

One other extremely helpful a part of rock mulch is its capability to drain water far more readily than wooden chips, straw, or leaves. Similar to grains of sand, rocks don’t have steady bonds that maintain in water and vitamins, and a few crops don’t wish to be in an space the place water retention exists. 

Smaller rocks are additionally nice for areas the place you wish to develop crops, however foot visitors might be heavy. By putting in rocks somewhat than mulch, you stop soil erosion under the mulch line. Regardless of the scale of rock you employ, when put in correctly, you may depend on it maintaining over time.  


View of a stone garden with growing decorative huja and pine, grass and shrubs. There are pebbles of different sizes and shapes in the flowerbed. Smaller ones cover the soil as mulch, while larger ones act as decorative elements of the garden.
Improper use of rock mulch, particularly bigger rocks, hinders plant development and irrigation.

All the issues with rock mulch originate from improper purposes. When you’re utilizing rocks bigger than ½ inch in diameter, you might be hindering your crops’ development. That is most typical when the rock mulch layer is simply too thick and might have the alternative of the specified impact.

In contrast to pure mulch sources, rocks aren’t porous. Water can stream round them, however until they’re lava rocks or pumice, water can’t stream by means of them. Even within the case of volcanic rocks, water doesn’t penetrate the mineral layers of the rock itself, solely seeping by means of the gaps and air bubbles left throughout the magma cooling course of. This will reduce efficient irrigation.

They warmth up a lot sooner than different natural supplies, probably damaging crops that want cooler temperatures. Which means sure rocks may be used for mulching crops that love scorching climate and dry circumstances. Nonetheless, the soil under could have bother retaining water, largely because of the radiant warmth from the stone inflicting soil moisture evaporation.


Rocks are heavy. An apparent drawback of utilizing rocks is having to maneuver them round in wheelbarrows and shovel them across the backyard. Reapplying layers of rocks is labor-intensive. Rocks are additionally far more costly than a free chip drop and even luggage of mulch.

You could have seen rocks utilized in landscaping round timber and shrubs. Whereas a skinny layer of small rocks is okay for this software, bigger rocks will disrupt the basis flare wanted to develop a wholesome tree. Attempt to keep away from these widespread errors when utilizing rocks within the backyard.

They don’t construct the soil. Most natural mulches will regularly decay, creating organically-enriched topsoil. In distinction, rock mulches don’t decay and don’t add natural matter to the soil. As that natural matter will help retain soil moisture and feed the soil’s microbiology, you might want to use a separate supply of natural materials, significantly to poor soils.

Lastly, the most important drawback with rock mulch is it’s not a sustainable supply of mulch. In comparison with chipped wooden, dried straw, and fallen leaves, they pale compared. That’s as a result of rocks are a non-renewable useful resource. They have to be mined or faraway from different soil and moved to a brand new location.

Kinds of Rock Mulch

Understanding the kind of rocks you want will enable you get probably the most out of a rock mulch. You need to decide which is finest in your backyard primarily based on their finest makes use of. However generally, it’s higher to keep away from rock mulch and select pure mulch as a substitute

Use your finest judgment, and bear in mind you could take away the rocks if you happen to discover they don’t work in your backyard. In that case, they might be utilized in areas the place crops aren’t rising. 

River Rocks

Close-up of river stones. River rocks are smooth, rounded stones that are naturally shaped by the flow of rivers and water bodies. These rocks come in various sizes, colors, and textures. They include shades of blue, gray, greenish and brownish.
Clean, multicolored river rocks sourced from waterways are pricey and impractical for plant development.

This sort of rock is mostly one to 2 inches in diameter and has a clean floor. This smoothness is attributed to publicity to operating water for a very long time. River rocks are sometimes sourced from rivers, stream beds, and seashores. 

They’re multicolored and excellent for areas the place you wish to fill in areas between bigger landscaping options. Construct ditches to direct water away out of your web site. After an extended set up of a dry creek mattress in one of many websites, it’s very satisfying to see what these rocks present.

Nonetheless, these will not be a good selection for rock mulch, as their measurement isn’t suited to rising crops. When you can set up them with absolutely grown crops, these crops could have a tough time pushing out new development amongst heavy rocks. Planting in a mattress of river rocks can be very laborious.   

Additionally, you will discover they’re more durable to supply than among the different choices right here. They’re additionally the second costliest of the alternatives on our record. 

Pea Gravel

Top view of a garden with Neoregelia carolinae plant growing. The soil is completely covered with Pea Gravel. Pea gravel is a small, smooth, and rounded gravel type characterized by its tiny, pea-sized stones. These small, naturally polished pebbles come in various muted colors, such as beige, tan, gray, or a mix of these shades. Neoregelia carolinae, commonly known as the Blushing Bromeliad or Neoregelia 'Tricolor,' is a captivating tropical plant prized for its unique appearance. This epiphytic bromeliad forms a rosette of broad, arching leaves that are glossy green with distinct banding of pinkish cream. The center of the rosette turns a vibrant pink to red.
Pea gravel, small rocks discovered close to water, is a budget-friendly mulch appropriate for arid gardens.

The smaller rocks you discover alongside seashores, streams, and river beds are what is called pea gravel. These are often not more than ⅜ of an inch in diameter. They have a tendency to have a barely wider vary of colours than river rocks, too, with extra tans and reds current. 

Pea gravel is a type of rock mulches that may work with rising crops in a backyard setting. It’s a good selection for a waterwise backyard in a scorching space, with native crops that admire the warmth and dryness. It’s not nice for a veggie or a shade perennial backyard, although. 

The best advantage of pea gravel is its value. It’s the most affordable on the record right here and straightforward to seek out in {hardware} shops and backyard facilities. 

Lava Rocks and Pumice

Close-up of a shovel pouring lava rock onto a flowerbed in a garden next to a green lawn. Red lava rock is a volcanic rock of a red-orange hue. Formed from the cooling and solidification of lava, these rocks exhibit porous and irregular surfaces, giving them a rugged and natural appearance.
Porous lava rocks and pumice are light-weight water-retaining mulches for heat-loving crops.

Each of those rocks are porous, which makes them distinct from the opposite rocks we’ve touched on up up to now. Which means they’ve the power to carry water in a backyard setting. They’re lighter than the opposite rocks on this record, too. It’s, subsequently, simpler to put in and regulate them.

Lava rocks are mined from historic, inactive volcanoes within the western United States. They aren’t technically lava however hardened magma. Pumice, alternatively, is sourced from the identical areas however is manufactured from the glassified froth of lava. 

When you’re working with crops that like warmth, these are helpful sources of mulch. Nonetheless, each sorts of igneous rock will be tough to plant inside. It could even be tough to take away fallen leaves from a backyard with volcanic rock, and garden tools will be broken by the arduous materials. 

Lava rocks are by far the costliest choice for rock mulch. That is most likely because of their capability to carry water and the truth that they’re more durable to supply. You will discover them in {hardware} shops and backyard facilities simply, although. 

Decomposed Granite

Close-up of decomposed granite. Decomposed granite is a granular material created by the natural erosion and weathering of solid granite rocks. It has a fine to medium texture, consisting of small, irregularly shaped particles that range in size from gravel to sand.
Decomposed granite, a typical pinkish igneous rock, serves effectively in xeriscaped gardens for decent climates.

This rock is derived from granite that has flaked away and takes on a gravely or nearly sandy texture. It’s a quite common igneous rock fashioned of the minerals feldspar, mica, and quartz. Granite is pinkish to peach-colored and comes from over 100 sources in the US.

That is the rock mulch most frequently employed in xeriscaped gardens. Similar to the others talked about right here, it will get scorching and drains effectively. Due to this fact, desert crops and different scorching climate crops that don’t wish to be waterlogged profit from it.

It has its advantages, however the small bits of decomposed granite can wash away in heavy rains if not put in in a successive and deliberate method. It’s simpler to arrange within the backyard because of its measurement, however you need to moisten every layer within the set up course of. 

You will discover decomposed granite in bulk or at an enormous field retailer with little situation. One other beauty of decomposed granite is that it’s the second least costly sort of rock mulch we have now mentioned. 

Remaining Ideas

Rock mulch is admittedly solely suited to a couple several types of gardens with hot-weather crops. Nonetheless, if you break it down, you’ve a number of sorts of rocks to select from, every with its personal advantages and pitfalls. Make the only option in your backyard, and benefit from the endurance. 

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