Organic mulch and rock are two popular ground cover choices for landscaping. Each has its own set of benefits and drawbacks. Rock is long-lasting, pest resistant, cheap, and low maintenance. Mulch helps to retain moisture, add nutrients to the soil, modulate temperature, and control weeds. In this guide, I’ll outline the pros and cons of mulch vs rock for landscaping to help you decide.
This choice comes down to the types of plants you’re growing, the climate, your budget, and your personal preference. I use both rock and organic mulch in my yard. In this guide, I’ll share my personal experience.
Pros of Organic Mulch
- Mulch adds nutrients to the soil- Over time, microorganisms in the soil break the mulch down. This releases important nutrients such as phosphorus and nitrogen into the soil. These nutrients increase soil health and fertility. This helps your plants grow faster and stronger. It also improves yields.
- Mulch adds organic material to the soil- Having organic material in your soil improves the soil structure and stability. The organic matter helps the soil absorb more moisture. It also helps to improve aeration and reduces runoff. This makes your soil more fertile.
- Water retention- Mulch reduces evaporation by shading the soil and blocking the wind. Organic mulch also absorbs some water. This helps the soil retain moisture for longer. In addition, mulching improves water infiltration. This moisture retention is particularly beneficial during hot or dry seasons. It helps with water conservation. You don’t have to water your garden as frequently. This saves you time. It also saves you money on your water bill. In addition, it makes your garden bed more drought-tolerant.
- Plants grow faster- According to this interesting article, mulching can double the speed of tree growth. Your plants will grow larger and faster and yield more when you mulch. This improves the efficiency of your garden. You can produce more food in less space.
- Fewer weeds- A layer of mulch reduces weed growth by blocking the sun from reaching the soil. This makes it harder for weed seeds that are in the soil to germinate. The weeds that do manage to germinate have a hard time growing through the layer of mulch. Mulching reduces the need for chemical herbicides. It can be even more effective if you install landscape fabric weed barrier before adding the mulch. This can also help keep the weeds down.
- Temperature regulation- Mulch acts as an insulator. It keeps the soil cooler in the summer and warmer in the winter. In the summer, it shades the soil from the intense sun to keep it cooler. In the winter, it creates a barrier between the soil and the snow and ice. This keeps your plant’s roots warmer. Mulch also helps to reduce temperature swings between the day and night. This can reduce stress on your plant. This is important if you live in an area that experiences extreme temperatures. Mulch will keep your soil just the right temperature.
- Affordable- Mulch is cheaper than rock. Many types of mulch are available for free including grass clippings, pine needles, dry leaves, and compost. You can use yard waste as mulch. If you have to buy mulch, it’s also pretty affordable. One consideration is that you have to replace mulch every year or so. Over time, mulching can become more expensive than rock. Particularly if you buy an expensive mulch like cedar*.
- Helps control erosion- Mulch helps prevent soil erosion by reducing runoff. The mulch absorbs part of the water. It also slows the flow of water over the soil so the soil and nutrients don’t get washed away.
- Reduces soil compaction- Mulch cushions the compacting force of rainfall, water from sprinklers, and foot traffic. When soil is too compacted, plants roots have trouble growing. Water and air also can’t pass through the soil easily. Mulch prevents this.
- Aesthetic appeal- Mulch can enhance the curb appeal of your home. It provides a neat and uniform look to your garden beds. It can also give your garden a more natural look. Mulch is available in a variety of colors and textures to suit your personal preference. Dyed mulch is available. Mulch can tie together walkways and flower beds. It’s beautiful.
- Easy to transport and install- If you have a small garden, you can simply buy mulch by the bag at a home and garden store. It’s easy to spread with basic hand tools such as a shovel and rake. If you have a large area to cover, you can have mulch delivered. Mulch is sold by the cubic yard.
Cons of Organic Mulch
- You have to replace organic mulch more frequently- Organic mulch breaks down over time. This mean it needs to be replaced periodically. On average, mulch needs to be replaced every 1-3 years. Some types last longer than others. Some need to be replaced twice per year. This adds work for you. You also have to factor in the replacement cost. If you’re looking for a long-lasting mulch, consider cedar chips.
- Mulch can attract pests- Some types of mulch can attract pests such as termites, cockroaches, centipedes, earwigs, slugs, snails, mice, and other critters that you don’t want in your garden. Rodents may hide and burrow in the mulch. It can be an ideal nesting spot. Mulch also holds moisture and heat that insects enjoy. If you have a pest problem in your garden, it’s best to stay away from pine straw, straw, hay, and shredded bark. Cedar and cypress mulch are great choices for those with pest problems. They naturally repel pest.
- Organic mulch is more expensive over time- As mentioned earlier, organic mulch needs to be replaced once in a while because it degrades away. Over time, the cost can add up. For example, maybe you have to buy 2 cubic yards of mulch every year to replace the mulch that has degraded away. This might cost you $100 per year. With rock, the initial cost is higher but you don’t need to replace it. You might spend $250 to place the landscaping rock then there are no recurring costs. Over the course of a decade, you might spend $1000 on mulch but only $250 on rock.
- Mulch can contain weed seeds- Some types of organic mulch, such as straw, hay, and compost, can contain weed seeds. When the weeds start to sprout, you have more work to do.
- There is a potential for mold, fungus, and disease to develop- In wet climates, mulch may retain moisture and never dry out. This can create an ideal environment for fungi to form. Various diseases can also spread in this environment. This is a common issue if you apply too much mulch. To reduce the likelihood of fungus and disease, you should never apply mulch more than 4″ thick.
- Some mulch can be displaced by wind and heavy rains- Lightweight mulches like straw or pine needles can be blown around in the wind. Some mulch might end up in your yard. The wind could also create bare spots.
- Floating mulches like wood chips can be displaced by heavy rain- They can float away if an area floods. After a storm, you may have to re-spread some of your mulch.
- Some types of mulch can be a fire hazard- Mulches, like pine needles or straw can be a fire hazard. These mulches will burn quickly if they catch fire. If you live in an area that experiences wildfires, you will want to use a mulch that isn’t as flammable near your home. You also should avoid these types of mulch near your barbecue or outdoor kitchen.
- Mulch can change color and become less attractive over time- When mulch is fresh, it has a vibrant and beautiful natural color. It might have a nice brown or orangish color, depending on the type. As it ages and weathers and begins to degrade, it can start to turn a dull gray, dark brown, or black color. It doesn’t look as nice. When the color fades, you’ll need to add a fresh layer.
- Timing is important with mulch- If you apply your mulch too early in the season, it can keep the ground temperature low and cause late blooms. If you apply it too late, you’ll have to deal with more weeds.
Pros of Rock
- Cheaper in the long run- The initial cost of rock is higher than mulch. Rock costs around $75-$250 per cubic yard depending on the type. To compare mulch costs around $30-$100 per cubic yard. The good news is that rock is a one time cost. It lasts pretty much forever as long as you clean it once in a while. Mulch needs to be replaced every year or two. If you plan on keeping your mulch for more than 2-3 years, rock is cheaper.
- Less maintenance- Rock does not need to be replaced like mulch. It doesn’t decay. Once in a while, you will have to clean it. Because rock is heavy, you can use a leaf blower to blow leaves, dust, and other debris out of it. You may have to add some rock every 5 years or so. This is because some rocks can get pushed into the soil below. This low maintenance makes rock a good choice for commercial properties. It takes much less time to maintain.
- Fireproof- One great feature of rock mulches is that they help make your home more fireproof. If there was a wildfire, it would have to jump over your garden to reach your home. This is a great feature if you live in an area that is susceptible to wildfires. This also makes it a great choice for areas around outdoor kitchens.
- It keeps the weeds down- Weed seeds that are under the rock have a hard time germinating because the rock blocks the sun. It is also hard for weeds to push through the heavy rock if they do manage to germinate. This reduces the need for herbicides.
- Rocks don’t get blown around in the wind- Rock is heavy, It won’t move around during windy days. You can also use a leaf blower on it without moving it around. This simplifies maintenance. It’s easy to blow leaves and other debris off of the rock.
- Pest Resistant- Unlike organic mulches, rock does not attract insects or rodents. This makes it a great choice for areas near homes. It won’t attract termites, like mulch can.
- Aesthetics- There are different types of rock that match different types of gardens. For example, you could use river rock, lava rock, crushed stone, and pea gravel. Rocks come in different colors. For example, lava rock comes in red, black, and gray colors. Rock can look great in desert environments like cactus gardens. It can add a nice finishing touch to your garden. Rock can also make a great backdrop for a water feature, fountain, or statue.
- Erosion control- Rock can be used on slopes to help stabilize the soil. It will stay in place on sloped yards. It has great drainage. Soil particles can’t wash away as easily when they’re covered in a layer of rocks.
- Durable- Rock can be a great choice for high traffic areas due to its durability. You can walk over it and drive on it without having to worry about causing damage. It’s a great choice for driveways or boat or RV parking.
Cons of Rock
- Difficult to remove- If you get tired of the rock mulch, it is a hassle to remove. You pretty much have to do it by hand with a shovel. Shoveling rock is a labor-intensive job, as you can imagine. Once you have the rock removed, you’ll need to load it and haul it somewhere to get rid of it. You’ll need a truck for this job.
- Higher initial cost- Rock is more expensive than organic mulch per cubic yard. On average, it costs about twice as much. It’s important to remember that rock is a one time expense while organic mulch is a recurring expense because it needs to be replaced as it degrades.
- Too much heat- Rocks absorb heat during the day. After the sun sets, they radiate heat for hours. This keeps the soil temperature too high. It can also speed up evaporation. This is important to consider if you grow heat-sensitive plants. Excessive heat can cause stress. It can also lead to thirsty plants if you don’t water often enough. Rock can also make your yard feel hot. On hot days, you may feel the heat radiating up from the rock. You won’t want to spend time in your garden if it’s too hot.
- Weeds will return eventually- Over time, wind will blow dust and soil into the spaces between the rock. Leaves, twigs, and other debris will break down and make their way between the rock. Weed seeds can blow in or be dropped by birds and other animals. When enough material accumulates in the rock, weeds will start to grow. To prevent this, you have to clean the rock. This is a big job. If you have lots of trees on your property, rock may not be the best choice because it will quickly fill up with leaves and debris.
- Rock can change the pH of the soil- Some types of rock can raise the pH of the soil to make it more alkaline. This is the case with carbonate rocks such as limestone. Most trees and plants prefer slightly acidic soil. They may not grow as well if the soil becomes too alkaline.
- Limited nutrient contribution- Rock doesn’t decompose and add nutrients to the soil like organic mulch. Over time rock can weather and release trace amounts of minerals into the soil. For example, lava rock contains magnesium, iron, and calcium. The amount of these minerals released will be negligible.
- Not suitable for all plants- Most plants don’t do well in landscape beds that are mulched with rock. This is because rock planting beds are warmer. The exception is succulents. These heat and drought tolerant plants can do well in rock beds.
- Uncomfortable to walk on- Some types of rock are sharp. You wouldn’t want to walk on them barefoot. They would hurt your feet. This is an important consideration if you have pets. Rocks can also be noisy to walk on.
- Hard to transport- Rock is difficult to transport because it is extremely heavy. You’ll probably have to get it delivered. If you want to remove it, you’ll have to hire someone to haul it away, unless you have a truck.
Types of Mulch and Rock
It’s also important to note that there are a number of different types of organic mulch including wood chips, bark, grass clippings, compost, sawdust, leaves, and more. Wood mulches such as wood chips and bark mulch can come from a variety of trees including cedar, spruce, pine, oak, and hemlock. Softwood and hardwood mulch are available. Wood mulches come in a range of textures including chips, nuggets, and shredded. A variety of colors are available as well including dyed mulch.
There are also a number of different types of rocks that can be used in your garden design including river rock, gravel, lava rock, and more. Rock comes in a range of colors, different sizes, and different textures. For example, smooth, gray river rocks and vibrant red lava rocks give your garden a completely different look. You can also use larger rocks and boulders to add a bit more texture to your garden.
Each specific type of mulch and rock has its own benefits and drawbacks. Check out my mulching guides for more info on specific mulches.
Final Thoughts
The choice between organic mulch and rocks comes down to the type of plants you’re growing, the aesthetics that you’re going for in your landscape design, and your personal preference.
Mulch is a great option for growing plants and vegetables because it provides nutrients and improves the soil structure. Rock is a better option if you’re looking for a low maintenance and durable ground cover.
Both mulch and rock can help control weeds, reduce erosion, and retain soil moisture. They can also look beautiful and the enhance curb appeal of your home. It’s always a good idea not to leave bare soil. Whether you go with rock or organic mulch, I hope this guide helps you make the right choice for your garden.
Do you use rock or organic mulch in your garden? Share your experience in the comments below!
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