Homesteading, Gardening, and Off-Grid Living

Rubber Mulch Vs Lava Rocks for Landscaping: Which is Best?

By: Zac Friedman

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When landscaping, it’s always a good idea to use some type of ground cover. Mulch can also suppress weed growth, retain moisture, reduce erosion, and insulate the soil. Most mulch is made from organic matter like wood chips, bark, straw, or pine needles. Synthetic or inorganic mulches can also be a good option because they don’t degrade over time. This guide outlines the pros and cons of rubber mulch vs lava rock for your vegetable gardens and flower beds. 

Rubber mulch is usually made from recycled car tires. The old tires are cut up into chips or strips. It can also come in rubber mats. Lava rock is a type of igneous rock that forms when lava cools. It is broken up and used as mulch. It’s a natural material. 

Both of these mulches are durable, long lasting, low maintenance, and pest resistant. Rock mulch is more environmentally friendly because it is a natural material. Rubber mulch is more comfortable to walk on and safer for kids to play on. 

Rubber Mulch Vs Rocks for Landscaping: Pros and Cons

Rubber Mulch Benefits

  • It’s long-lasting- It doesn’t degrade over time like organic mulches. A layer of rubber mulch will last for up to a decade without any signs of degradation.
  • Cheaper- Initially, rubber mulch is cheaper than lava rock. It doesn’t last quite as long so it might be more expensive if you plan to keep it long term. It will need to be replaced around once every 10 years. 
  • Rubber mulch comes in a range of textures- It can be cut into chips or strips of different sizes. It also comes in mats. Rubber mulch can look like wood chips from a distance.
  • It’s available in different colors- Most rubber mulch is black but it is also available in red, green, blue, purple, and multi-color. Red mulch can contrast nicely with green plants. Brown mulch can look more natural. Black mulch is the most common because that is the color of cut-up tires that are often recycled into mulch. 
  • It tends to stay in place- Rubber mulch won’t blow away on windy days. It also won’t float away if you experience flooding because it is such a dense material. This makes it a good choice for sloped gardens. 
  • Helps control weeds- Rubber mulch is pretty heavy. It’s hard for weeds to push through after they germinate. Rubber mulch also blocks weed seeds from reaching the soil. This helps keep the weeds down.
  • Low maintenance- Rubber mulch is heavy enough that you can use a leaf blower to clean it. This makes it easy to remove leaves and other debris. You don’t need to add mulch because it doesn’t decay. 
  • Resistant to soil compaction- Rubber mulch can absorb impacts from foot traffic and heavy rains. You can drive and park on it. It stays on the surface of the soil. It doesn’t need to be topped up. 
  • Pest resistant- Unlike organic mulch, rubber mulch does not attract insects or rodents. This makes it a great choice for areas near homes. It won’t attract termites, ants, or mice. 
  • Durable- Rubber mulch 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 walkways, driveways, playgrounds, or boat or RV parking.
  • It’s safe to play on- Rubber mulch is a great choice for kids’ play areas. It does a great job of absorbing impacts. If kids fall on it, they won’t get injured. It also won’t cause slivers, like wood mulch can. You can walk on it barefoot without hurting your feet. If you’re building your kids a swingset, consider putting rubber mulch under it. For more info, check out my guide: rubber mulch for wood chips for playgrounds.
  • Erosion control- Rubber mulch slows the flow of water over the soil so the soil and nutrients don’t get washed away.
rubber mulch on a playground
Playground rubber mulch

Drawbacks of Rubber Mulch

  • It’s not environmentally friendly- Over time, the rubber can break down into tiny particles and contaminate your soil. These tiny particles are called microplastics. Over time, these microplastics can make their way into waterways where they can harm marine life. Rubber mulch made from old tires can also contain a number of harmful compounds, such as zinc and heavy metals, that you don’t want in your soil. These compounds can leach into the soil where your plant roots can pick them up. Zinc has been found to stunt plant growth. For this reason, it’s best not to use rubber mulch in your vegetable garden. You don’t want it near anything you plan to eat.
  • Rubber mulch also does not add any nutrients to the soil because it is not an organic material- Organic mulches, like wood chips or straw, can add valuable nitrogen and phosphorus. They can also add organic matter which helps the soil retain more moisture. This is useful if you have sandy soil. Rubber mulch won’t improve soil quality at all. In fact, it will just make the soil quality worse by adding contaminants from the rubber.
  • It’s not a great choice for areas prone to wildfires- Rubber will burn very hot if it catches on fire. If you live in an area that is susceptible to forest fires, you’re better off with rock mulch. 
  • It can be difficult to remove- Over time, rubber mulch can mix with your soil. Because it doesn’t degrade, it will just stay there. The best solution is to use a layer of landscape fabric between the rubber and the soil. 
  • Aesthetics- From a distance, rubber mulch looks like wood chips. Up close, it’s obvious that it isn’t a natural material. It has a kind of shiny appearance. Many people prefer natural materials like organic mulches or rock. 
Lava rock mulch

Lava Rock Pros

  • Fireproof- One great feature of lava rock and other types of stone mulch is that it helps make your home more fire-resistant. If a wildfire were to reach your property, it would have to jump over your rock garden to reach your home. This is important if you live in an area that is susceptible to wildfires. Lava rocks are also a great choice for areas around outdoor kitchens for the same reason. They don’t burn.
  • Low maintenance- Rock mulch doesn’t need to be replaced like organic mulch. It doesn’t degrade. Once in a while, you will have to clean it. If you don’t leaves and dirt will accumulate and weeds will start growing. You can use a leaf blower to clean off the rocks. You may need to top it up once in a while because the rock can get pushed into the soil.
  • Pest resistant- Lava rock does not attract pests such as rodents, termites, ants, snakes, etc.
  • It lasts a long time- Volcanic rock doesn’t degrade over time. It will last pretty much forever as long as you use landscaping fabric to prevent it from mixing with the soil. This makes it a great choice for commercial properties. 
  • Helps retain soil moisture- Lava rock is a porous material. The rocks contain air pockets. This allows the rocks to soak up water and release it over time. A layer of rock also shades the soil, which slows down evaporation. You won’t have to water as often. This is good for water conservation. You’ll also save money on your water bill. If you’re trying to build a drought-tolerant garden bed, lava rock is a good choice.
  • Helps suppress weeds- Lava rock can act as a weed barrier. The rock blocks the sun to prevent weed seeds in the soil from germinating and growing. It also makes it difficult for weeds to push through to the surface. In addition, it prevents weed seeds that blow in from reaching the soil surface. You won’t have to use as many herbicides. It can be particularly effective when you install landscape fabric underneath.
  • Helps insulate the soil- Lava rock can help regulate soil temperature. During the day, lava rocks absorb heat from the sun. At night, it can pass this heat to the soil. This helps keep the soil warmer. This can reduce the temperature swings between the day and night, which reduces stress on your plant’s roots. Lava rock also helps your plants roots stay warmer in the winter by creating a barrier between the snow and ice and the soil. This is important if you live in a particularly cold climate. 
  • Lava rock looks better- Lava rock is a natural material. Most people find natural mulch more attractive than synthetics, such as rubber. Lava rock is available in several colors including red, brown, and black. Red lava rock is probably the most popular. Black lava rock can look beautiful as well. The color won’t fade over time. Different sizes are also available. Lava rock can go really well with certain landscape designs. For example, it looks really nice in desert environments. If you don’t like the appearance of lava rock, there are other types of rock mulch to consider such as river rock or pea gravel. 
  • It’s environmentally friendly- Lava rock is a completely natural material. It doesn’t add any chemicals or contaminants to your garden beds. This is the biggest benefit of natural products. 
  • Erosion control- Lava rock can be used on slopes to help stabilize the soil. It offers good drainage. It also absorbs some water, which reduces runoff. It helps to prevent soil particles and nutrients from washing away.
  • Durable- Lava rock can be a great choice for high traffic areas due to its durability. You can walk over it and drive on it without causing damage. It’s a great choice for driveways or RV parking.
A cactus garden with lava rock
Desert-themed gardens look great with lava rock.

Lava Rock Cons

  • Higher initial cost- Lava rock can be more expensive upfront than rubber mulch. Lava rock can cost anywhere from $100-$250 per cubic yard. Lava rock can last longer than rubber mulch so it can be cheaper in the long run if you plan to keep it for more than a decade or so. 
  • Lava rocks can absorb and radiate heat- During the day, the sun can heat the rocks up. This heat can radiate up from the rocks and make it feel hotter in your yard. It can even heat up your home. The excessive heat can be hard on plants. The heat can also speed up evaporation so the soil dries out faster. You may have to water more often when it’s hot out. This can be a problem if you live in a particularly hot area or if you have heat-sensitive plants. It also makes your yard less comfortable.
  • Lava rocks don’t provide many nutrients- Lava rock doesn’t decompose like organic mulch. It won’t release any nutrients into the soil. Over time, lava rock can weather and release some minerals. Lava rock contains minerals such as magnesium, iron, and calcium. The amount released will be pretty negligible.
  • Can be difficult to remove or replace- Lava rock can mix with the soil over time. When you walk on it, it can get pressed into the soil. This makes it difficult to remove. This can be an issue if you ever plan to change your landscape design. One solution is to lay landscape fabric under the lava rock. This can help prevent it from mixing with the soil. Landscape fabric has its own drawbacks to consider. 
  • It’s uncomfortable to walk on- Lava rocks have a rough texture. You won’t want to walk on them barefoot. They have sharp edges that can hurt your feet. Your pets may not feel comfortable walking on it either. Kids won’t want to play on it. Lava rock can also be noisy to walk on. It’s not a great choice for walkways.
  • Lava rock is difficult to keep clean- Over time, debris such as leaves and sticks will get caught in the lava rocks. Dust and dirt can also blow in and get caught in the holes in the lava rock. This makes your garden look messy. Smaller lava rocks will blow around if you try to use a leaf blower. Over time, leaves and debris can degrade into soil. Eventually, weeds will start growing in your lava rock. 
  • They don’t look good with some landscapes- Lava rocks have kind of a distinct look. They don’t go with all homes and landscape styles. Some people just don’t like the aesthetics. 
  • It can raise the pH of the soil to make it more alkaline- Lava rock releases some minerals that can make your soil more alkaline. This can be a problem if you grow plants that prefer more acidic soil. They may not grow as well if the soil becomes too alkaline. Usually, the change in pH is negligible. 
  • It can be displaced by high winds- Because lava rock is so light, extreme wind can blow it around. This is rarely an issue unless there is a major storm. 
Lava rock garden

Final Thoughts

If you’re looking for a durable, long-lasting, and low-maintenance mulch, you can’t go wrong with rubber mulch or lava rock. 

The main drawback of rubber mulch is that it isn’t the most environmentally friendly material. It contains some toxic chemicals that can leach into the soil. It can also produce microplastics. You don’t have to worry about this with lava rock. 

To me, lava rock is the better choice. It may be slightly more expensive initially but it has a more natural look and it is environmentally friendly. It will last longer as well. Rubber mulch can be a great choice for children’s play areas because it provides lots of cushioning. 

Organic materials can make better mulch for vegetable gardens because they can add nutrients to the soil as they degrade. They can also introduce organic matter to the soil which improves soil structure. This will increase yields. Some great organic options include wood chips, bark chips, pine straw, grass clippings, and compost. There are lots of different types of mulch to choose from. I’m a big fan of cedar mulch. 

Whichever type of mulch you choose, I hope this guide has helped you in making your decision. 

Do you prefer rubber mulch or lava rock? Share your experience in the comments below!

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Rubber Mulch Vs Rocks for Landscaping: Pros and Cons

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