Lava Rock vs Rubber Mulch

A closeup of lava rock mulch.

lava rock and rubber mulch are inorganic mulches that add a clean landscaped look to any yard. Because they are inorganic, they will not add any nutrients to the soil like wood or straw mulch would. However, both lava rock and rubber mulch last years as opposed to months. Mulches composed of rubber are manufactured from recycled tires, while lava rock is a lightweight material mined from volcanic deposits.

TIP: Our expert gardening advisor, Rachel Klein adds, "Inorganic mulches are a perfect addition to public or show gardens because it can literally be made to order in a number or colors, sizes, and textures."

Lava Rock

Lava rock comes in both red and black. Because it is lightweight, it is inexpensive to have shipped to you and simple to spread on your beds. Lava rock absorbs heat during the day and releases it at night, keeping your plants at a consistent temperature. It also prevents evaporation from the soil, keeping it moist longer. If installed with a weed barrier, such as landscaping cloth, lava rock acts as an effective weed prevention method. Some downsides include potential damage to lawn mowers and other gardening equipment if they come in contact with the rocks. Landscapers advise setting the rocks an inch or 2 below the sidewalk level to restrict their movement. This mulch can be found in some garden supply stores or can be ordered online. Lava rock makes a beautiful statement, especially when used in permanent beds or desert and rock gardens.

Rubber Mulch

Rubber mulch is recycled chunks of chopped up tires. It can be found in nugget or shredded form. Although that doesn't sound too appealing written down, this mulch looks very attractive spread over a permanent bed. Rubber mulch offers garden soil the highest insulation from heat of any other mulch. This mulch keeps the soil moist while preventing weeds from germinating. Rubber mulch is not toxic, but it is argued that it may release chemicals into the water that can negatively impact wildlife. Because of this, it should not be used in close proximity to bodies of water, such as ponds. One of the greatest advantages of rubber mulch is its springy texture. Comfortable to sit, kneel, or even lay on, this mulch is ideal for playgrounds, paths, and even horse arenas. If sitting on the hard ground to garden is a major detractor for you, this mulch could be the perfect addition to your landscaping.

Lifespan Comparison

It is usually claimed by manufacturers that their rubber mulch will last for a minimum of 10 years. However, rubber mulch does break down with time, and needs replacement eventually, typically after 5 years or so. Lava rocks do not break down and can last a lifetime.

Best Uses of the Materials

Lava rock and rubber mulch can be laid on landscape fabric for optimum weed prevention. This also makes it easier to pull the mulches back for planting or soil amending. Both mulches are best used in beds that require little maintenance and are rarely disturbed because removing them can be time consuming.

Advantages of the Mulches

Rubber mulch is made from recycled materials. This greatly reduces our carbon footprint and makes use of materials that would otherwise end up in a landfill.]Lava rock on the other hand is more natural since it is mined from volcanic deposits. Lava rock is certainly more expensive than rubber mulch, but also lasts longer and offers a beautiful texture. Neither mulch gets blown away in strong wind or float out when it rains unlike kinds of organic mulches.

TIP: Rachel suggests, "If you are a no muss no fuss kind of gardener, one of these great options could be ideal for you."