According to the Rubber Manufacturers Association (RMA), of the 270 million scrap tires generated annually, at least 15 million are processed into ground rubber, or "buffings." These buffings are what is used to make the rubber landscaping mulch you've probably seen for sale recently in home improvement centers.
Several companies are now in the business of making rubber mulch and offer it in a variety of colors, including green, blue, black and terracotta. You can find it in either chunk or chipped form. Popular brands include American Rubber Technology's Rubberstuff® and Dupont's Garden Products Long-Lasting Mulch.
So what are the claims being made about rubber mulch and how does it compare to wood mulches? Here are some pros and cons:
- Won't break down and in most cases is guaranteed to last 10+ years
- Won't float or blow away
- Is non-porous, so water and wet fertilizer applications will pass right through to the soil below
- Suppresses weeds
- Can be used against the house, thus discouraging wood-eating insects
- Non-toxic and non-flammable
- Does not add organic matter to the soil
- Landscaping grade rubber mulch can contain wire
- Costs more (initially)
- Can be smelly for a brief period upon application
Some of the "pros" listed above are not without controversy. There is concern that rubber mulch does indeed leach zinc into the soil in small amounts and can cause an imbalance in soil alkalinity. A few gardeners have reported that after rubber mulch was placed around landscape plants, the plants died.
I'll have to admit I was wary about this stuff. However, my mind was changed somewhat after a dilemma I faced with my sunroom.
I have a "live" solarium in my house; that is, there are palms and other tropicals growing right up through the floor around the border of the room. For many years, this area was mulched with standard wood chips.
Well, after awhile the wood mulch started to break down, as it should. That's fine if you're outside. But indoors, the gases released by decaying mulch can be smelly and harmful. So I figured...what about this rubber mulch thing?
I wasn't terribly concerned with enhancing the soil quality - it's mostly builder's sand underneath and the plants seem fine with that. In this case, rubber mulch was the perfect answer.
After scraping off what was left of the old rotted wood mulch, I bought four bags of Rustic Red Rubberstuff® and applied it. And I must say, it looks good, doesn't smell and seems to stay put (except when my collie decides to do some digging.) The mulch has been in place for about six months and my plants do not show any ill effects.
As an organic gardener, I'll probably never use rubber mulch in my yard. Although it apparently does eventually break down after 25 years or so, I just don't like the thought of all that rubber (and some wire) being in the soil that I've tried so hard to improve by natural means.
That's not to say rubber mulch isn't handy for some tasks. The wire-free type is currently being used by many schools and municipalities for the surfacing of playgrounds. It is also gaining popularity as a softer surface for sports fields, military training bases and equestrian arenas. The question still remains about leaching, however. Are our waterways being polluted? Is the soil becoming unbalanced?
Weigh the pros and cons for your own landscaping needs, but know this: we'll be hearing more about rubber mulch in the future, one way or another.