Pros And Cons Of Using Lava Rocks As Mulch In Your Garden

A careful look at garden beds while walking shows that more and more often used as a layer of mulch exotic-looking gravel. These are lava stones, which offer many advantages as mulch.

  • Lava mulch is a natural product
  • well suited alternative to bark mulch
  • has many advantages, but also a few disadvantages

Lava mulch

Lava mulch, also called lava gravel, is nothing more than solidified lava rock. It is therefore a natural product. Lava is formed when a volcano spews magma or liquid comes to the earth’s surface. Flowing as well as solidified lava is called lava flow. This is mined and processed into lava mulch. Since lava rock is also mined in Europe, you do not need to resort to a product with long transport routes.


Lava gravel has a number of advantages, but is also associated with disadvantages especially if the mulch of lava stone is used in the wrong places in the garden.


In order for lava granules to develop their beneficial properties optimally, the applied layer should have a thickness of six to eight centimeters.

Advantages for gardening

Structural stability

If the bed has to be stepped on during gardening, pressure is exerted on the soil. As a result, it becomes compacted, which negatively affects the water and air balance of the soil and harms the bedding plants. This problem can be solved with lava chippings, because it removes the pressure that occurs during walking, so there is no soil compaction.

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Rindenmulch ausbringen

Since lava gravel does not rot or degrade, you do not need to renew the mulch layer annually.

Note: If after a while you find that you don’t like lava mulch in the bed, you don’t have to remove it, you can dig it under.


Because wet bark mulch is slippery, accidents can easily occur after a rainstorm when the mulched garden bed must be walked on. With lava gravel, there is no such danger. Plus, your gardening shoes stay clean because the rock doesn’t get slippery or dirty from the soil.

Weed reduction

The quick drying of the lava mulch layer worsens the establishment of weeds that start to grow. But also for other undesirable plants the growing conditions are bad, because their roots hardly find a hold on the granulate.

Advantages for bedding plants

Water balance

Nasser Rindenmulch

Lava grit reduces water evaporation at the soil surface and prevents the upper soil layer from drying out. This leads to the fact that the soil is better aerated. Since the surface of lava rock dries very quickly, the risk of viruses, bacteria or fungi becoming established in the moist environment of the mulch is reduced.

Nitrogen content

Since lava rock mulch does not rot, it does not consume nitrogen from the soil. Therefore, nitrogen top dressing is not necessary.

Temperature regulation

Lava rock keeps the soil cool and moist in summer. In winter, it protects the soil from cooling down as it warms up during the day and releases the heat to the bed soil during the night.

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Lava mulch is available in black, gray and brown tones, which significantly increases the design scope compared to bark mulch. Another visual element is the grain size. However, you should not use one that is too large, as this will make it more difficult to plant new plants. Ideal grain sizes are

  • two to eight millimeters or
  • eight to twelve millimeters

Note: You can also mix different grain sizes to create a special effect.


Although lava granules can be used for useful and ornamental plants, it is not suitable for all places in the garden. For example, you should not apply it under trees or deciduous shrubs, which is difficult to remove the fallen leaves from the mulch layer.


Since this also applies to cut grass, you should not use lava granules in the immediate vicinity of the lawn. Also, smaller particles of lava that get on the lawn can damage the lawn mower.


If weeds settle between the lava particles, for example because the granulation has been chosen too large, they are very difficult to remove. In addition, the top layer is destroyed by the unwanted plants, which means that the mulch layer has to be straightened again.

New plantings/redesign

If new plants are to be added to the bed, insertion is very difficult with an existing layer of lava mulch, as the particles cannot be easily pushed aside. Therefore, you should plan well in advance a garden bed on which you want to finally spread lava particles.

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Lava chippings usually cost a little more than conventional bark mulch, but this is offset by the durability of the material.

Frequently asked questions

Can I use lava rocks for potted plants?

Yes, the lava mulch is also suitable for pot culture without any problems.

Can lava gravel prevent waterlogging in the soil?

Lava stone ensures that rainwater can drain away well. It is said to have the same effect as drainage in the soil.

Can I spread lava granules in the rock garden?

Yes, lava rock is suitable for mulching rock or prairie gardens.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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