Rubber Mulch Vs. Wood Mulch

The choice between using rubber mulch or wood mulch in your garden comes down to some fairly significant issues including toxicity, the possibility of infestation, benefits for the soil and the overall cost in terms of labor and out-of-pocket expense. Contrary to popular belief, both types of mulch have the ability to leak toxins into the soil making it necessary to carefully weigh the potential benefits and liabilities of each product. 

What’s This About Toxicity?

While both wood chip mulch and rubber tire mulch can provide excellent weed control, conserve soil moisture and look good doing it, they  have one other issue in common. They both can deliver toxins into the very soil they are meant to protect. Most rubber mulch consists of ground up tires that have gone out of commission. This means that while the rubber alone can leak zinc into the soil below, other chemicals that these well worn tires have come into contact with in their travels may also have come along for the ride and could present a problem. However, rubber tire mulch is not alone in this respect. Wood mulch can be just as problematic if it consists ofany wood other than tree bark. Wood mulch products often use dyed woods, old pallets that have been ground up and other woods which were used in industrial capacities. These woods may contain arsenic and creosote among other byproducts. Because wood and rubber mulch can both be toxic for plants and ground soil, one does not easily come off as a better choice than the other.

Do Both Types Of Mulch Pave The Way For Infestation?

When it comes to insect infestation, rubber mulch wins the day. Rubber mulch does not attract termites because it is not made of the kind of organic material they like to travel through and settle in. Furthermore, if you are worried about a mold infestation, rubber mulch might be best for you. Rubber tire mulch reduces mold and weed growth by dehydrating most weed seeds and spores before they can reach through to the soil. Wood mulch, on the other hand, can allow for the infestation of both termites and fungal growth. Termites love to settle in and travel through wood mulch as it is so full of the food they crave. On top of this, wood mulch can breed "artillery" fungus that can stain nearby cars and homes with fungal spores that, once dried, remain forever.

Doesn’t Wood Mulch Benefit Soil More Than Rubber?

This depends on the types of benefits you are looking for. Rubber mulch provides excellent drainage for the soil and supplies great insulation against harsh weather. It allows a higher degree of heat to be maintained in the soil as well as maintaining its moisture levels. Wood mulch, however, can actually starve plants. Wood chip mulch is high in carbon which seeks out nitrogen to help it break down into soil. In doing so, it effectively steals the food from the plants it’s meant to protect.

How Do The Overall Costs Compare?

Given that rubber mulch lasts longer and does not require yearly re-spreading or repurchasing, even its relatively high cost per bag is made up for by its longevity. Wood mulch fades, requires repurchasing every one to two years and can cause termite troubles which would only increase labor and out-of-pocket costs.

According to the criteria laid out here, one would have to give rubber mulch very serious consideration despite the many chemicals that go into the production of tires.