Rubber might not be the first thing that comes to mind when you think of mulch, but this material’s been gaining popularity for a number of reasons. It’s long-lasting, stays in place, and doesn’t attract bugs. Because this mulch is made from recycled tires, though, there are some concerns about how healthy it is for your soil and plants.
Pros: A Low-Maintenance Way to Protect Plant Roots
Rubber mulch will stay in place for years to insulate plant roots from heat and cold, keep down weeds, and discourage pests.
Requires Little Maintenance
Because it breaks down so slowly, rubber mulch will look much the same year after year even with next to no maintenance. While some cheaper dyed mulches might fade, many brands are rated to keep working and looking good for at least 10 years. Unlike with most organic mulches, you won’t have to replace rubber mulch every year or two, so you’ll save both time and money.
Won’t Drift Away
Rubber mulch is heavy enough that it won’t easily float or blow away. If your planting bed becomes flooded from rain or over-enthusiastic watering, pine straw, and wood chips are likely to float and drift so much you’ll need to rake the mulch back into place. Strong winds and leaf blowers can do the same to lightweight organic mulches. If you live in a storm-prone area or you use wind-generating garden equipment, rubber mulch can save you some cleanup work.
Doesn’t Attract Pests
Mulch made from wood tends to attract pests such as carpenter ants, termites, and wasps, which limits where you can use these mulches. Pests like these avoid rubber mulch. You can safely use rubber mulch near your home’s foundation or around outbuildings without worrying you’ll end up with termites. In fact, rubber mulch helps protect your buildings from wood-eating pests, so you can use less pesticide.
In summer, mulch protects your plants’ roots from heat and dehydration, while in winter, it defends them from frost. As a highly effective insulator, rubber mulch is one of the best materials you can use if your goal is to protect your soil and plant roots from the elements. If you live in a hot climate, avoid dark colors of rubber mulch, which absorb heat and can overheat the soil.
Inhibits Weed Growth
Holding weeds down is one of the main purposes of mulch, and rubber mulch does this job reasonably well. While it’s a viable solution to weed control, it’s not quite as effective in the long term as organic mulches.
To really control weed growth with rubber mulch, you’ll need a layer of at least 2 inches or preferably 4 inches. Rubber mulch won’t hinder seeds and young weeds already in the soil, so remember to weed or till the soil before you mulch.
Improves Safety in Play Areas
The density and resilience of rubber mulch make it perfect for protecting children from falls in play areas. Rubber mulch is clean, so it won’t stain your kids’ clothes, and it stays in place so your kids won’t be tracking it into the house. Just make sure you get the wire-free variety. For effective shock absorption, install a layer of at least 6 inches.
Cons: High Purchase Costs and Potential Soil Contamination
Despite being a recycled material, rubber mulch doesn’t come cheap. What’s more, some of the chemicals and metals used in the tires that make rubber mulch are a potential source of soil contamination.
Costs More Up Front
Rubber mulch is considerably more expensive than organic mulch. Most brands will run you more than $10 per cubic foot, and some are as much as $15 per cubic foot. Then add in the cost of the landscaping fabric you’ll need to lay under this mulch.
To compare, pine straw typically costs around $5 or $6 per cubic foot, and naturally colored wood chips can be had for around $2 per cubic foot, although dyed varieties are more expensive. Straw costs even less than these, but you’ll need to replace it every year.
While rubber mulch does last longer, it takes around six to eight years for the average homeowner to recoup their investment. If you don’t mind using the same rubber mulch that long, it’s an economical option. Just beware of cheap rubber mulches, which are often made from radial tires and might still have bits of wires inside. Wire-free mulch costs more.
Poses a Minor Fire Hazard
Because rubber mulch contains petroleum, it’s more likely than organic mulch to catch fire from a flame or heat source, such as a cigarette butt or tipped-over garden lantern. If it does, it will burn faster and hotter, be harder to extinguish, and release thick smoke laden with harmful chemicals. While there’s little risk of your mulch catching fire, it’s something to consider if you’re looking for a material that’s safe to use around open flames.
Difficult to Remove
Before you use rubber mulch, you’ll need to lay down landscaping fabric to keep the mulch separate from the soil. That’s because once chunks of rubber mulch get mixed in with the soil, they’re nearly impossible to remove unless you pick them out by hand. In fact, you might need to remove the entire top layer of soil to get all the rubber out.
This makes weeding harder, too. Rubber mulch doesn’t biodegrade quickly and doesn’t add nutrients to the soil, so you can’t till it into the soil to get rid of weeds. If weeds pop up, you’ll need to pull them by hand.
Can Release Harmful Metals and Chemicals
When heated by the sun, rubber mulch can release chemicals known as volatile organic compounds (VOCs). Not only do these fumes often smell bad, they’re also bad for your health. If you live in a climate with hot summers, avoid using rubber mulch around seating areas where you don’t want the smell of hot rubber.
Worse yet, this mulch can leach heavy metals such as aluminum, zinc, cadmium, and chromium into the soil and eventually the groundwater. In particular, rubber from tires contains a high level of zinc oxide, which can accumulate in your plants and eventually kill them. This is even more of a problem in areas where the soil is already rich in zinc, so it’s a good idea to have your soil tested before you apply rubber mulch.
Durable, easy to care for, and an excellent insulator, rubber mulch is a practical choice for beds with mature shrubs or trees. Its soft, springy texture also makes it useful in children’s play areas. For flower and vegetable beds, though, it’s less than ideal. Smaller plants are more vulnerable to the chemicals and metals rubber mulch releases into the ground and vegetables can absorb these contaminants.