Rubber mulches are used both as a soil cover and underneath artificial turf. Is this a good idea? According to “Garden Professor” Linda Chalker-Scott, the answer is no. She has a new fact sheet on the subject which concludes,
Rubber mulches can be attractive, easy to find and apply, and may not need frequent re-application. However, there are significant problems associated with using these mulches. In the short term, rubber mulch is not as effective as other organic mulch choices in controlling weeds. Furthermore, rubber mulches can attract insects (e.g., cockroaches), and they are highly flammable. In the long term, decomposing rubber mulch releases heavy metals and organic chemicals with unknown effects on human and environmental health. Other organic mulch choices, especially wood chips, are better performers and pose none of the environmental risks attributed to rubber mulch.
One of the principle plant toxins leached by rubber mulch is zinc. We have personal experience with zinc phytotoxicity in our own yard due to air pollution in Los Angeles (many years worth of brake linings blowing around and settling on the soil). I suspect that many of our gardening frustrations are related to our zinc problem.
I’d add that the other obvious disadvantage of rubber chips is that they don’t break down to build soil–and they don’t invite in the fungi, either, which is critical to plant health.
Also, I’ve never understood how people keep artificial mulch clean. What happens when leaves fall on it? With wood mulch it all just sort of blends in.
It has never occurred to me to use rubber tires as mulch, but I am curious about zinc toxicity… I see a lot of galvanized containers being used to grow flowers and garden crops, and have not been able to find good information about if food grown in a zinc container is safe to eat… I am referring to the somewhat trendy use of metal livestock watering tubs and troughs in urban gardening
Zinc is a nutrient for people (in small quantities). The problem is more for plants.
People actually do that? I would imagine that a shredded rubber mulch would absorb and radiate heat, and give off an unpleasant smell.
I’ve seen in mostly in “kid friendly” applications–under swingsets and such.
Rubber mulch may actually be the one material worse than river rock.
It does not build soil through decomposition because it does not decompose the way a natural mulch would.
It can leach chemicals and pollutants depending upon the type of tires used and the manufacturing process. Not to mention the dyes and colorants used to make that nice bright red mulch that seems to be de riguer in parade homes.
Ugh.
I’ve also seen recommendations that whole tires don’t pose a problem in the garden, but I’m not sure I wholeheartedly agree. Certainly whole tires leach contaminants more slowly than shredded rubber, but I would not call that report conclusive evidence that whole tires are safe.
But I also have to admit that I’m definitely biased in favor of garden materials that break down into nice clean dirt.
As I walked through a garden center last week, the inside of my nose was irritated and there was a horrible smell. As I looked to one side, there were products made of tires, the round circles to put around trees to keep down weeds and facilitate mowing. People have assured me tires are okay for planting potatoes, but I am not giving in to that convenience.
All those odors are filtered through my liver, so I just refuse to use tire products except on my car.