Rubber Mulch Vs. Lava Rock


Rubber and lava rock are inorganic mulch materials that do not add nutrients to the soil or improve the soil composition. They are difficult to remove when making changes to the landscape.


Rubber mulch maintains warm soil temperatures. Lava rock absorbs heat during the day and releases it at night which speeds up water loss.

Time Frame

Rubber mulch is broken down by microbes and needs replacement every couple of years. Lava rock does not decompose, so it does not require annual replacement.


Rubber mulch is not safe to use in gardening or landscaping in areas near water. Lava rock is best in rock gardens, herb gardens and Japanese designs.


Rubber mulch is not toxic, but it contains substances that can leech into the water system and negatively impact wildlife. Lava rock is expensive, but is one of the longest lasting mulches.


Rubber mulch is likely to ignite when contact with flame is made and it is difficult to extinguish.


  • The Myth of Rubberized Landscapes
  • Miracle Mulch
  • A Guide to Mulches

Who Can Help

  • Mulches Fact Sheet
Keywords: inorganic mulches, rubber mulch, lava rock mulch

About this Author

Karen Carter has spent the last three years working as a technology specialist in the public school system. This position included hardware/software installation, customer support, and writing training manuals. She also spent four years as a newspaper editor/reporter at the Willapa Harbor Herald.