My Brother-in-Law uses rubber mulch in his gardens, but it concerns me. What are your thoughts? Thank you. Mary Ellen
Answer
My short answer is that I would never use it or encourage you to use it. It may sound like a good use for recycled tires, but there are enough definitive studies that have been done to convince me that it is a bad idea. Organic mulch serves several purposes in the garden: a thick layer will deter weed growth, keep the soil cool and moist and as organic mulch decays adds valuable organic matter to the soil. As far as weed growth is concerned, Consumer Reports did comparative testing some time ago and concluded there wasn't much difference between rubber and organic mulches. Their results were partially contradicted by horticulturalist Linda Chalker-Scott, Associate Professor and Extension Horticulturist at Washington State University, whose research showed in the long-term rubber mulch was not as effective as organic mulch in weed control. She also pointed out that one big deterrent to using rubber mulch is its flammability. Consumer Reports echoed her concerns in their testing that showed that rubber mulch (which contains petroleum products) burned faster and much hotter than organic mulch and was harder to extinguish. Organic mulches are more difficult to ignite initially and they burn slowly because of their low carbon to nitrogen ratio. Ms. Chandler-Scott also is concerned about rubber mulch's toxicity. The rubber eventually breaks down and releases heavy metals and other harmful chemicals into the soil and eventually into the water supply. Of particular concern to Rufus Chaney, an Environmental Chemist at U.S.D.A, and others is that small amounts of the heavy metal zinc in tires will eventually leach into soil at levels sufficient to kill plants.
My advice is not to use rubber mulch. If you are concerned about the amount of organic mulch you need in your gardens, there is a safer approach. When I design and install gardens, I always use a ground cover layer, in addition to layers of perennials, shrubs and trees. As ground covers grow, you will need less and less mulch each year. There are many wonderful ground covers to choose from that do well in our area. Get in touch with me if you need help with ground covers.
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About Linda Lillie
Linda K. Lillie is the President of Sprigs & Twigs, Inc, the premier
landscape design and maintenance, tree care, lawn care, stonework, and carpentry
service provider in southeastern Connecticut since 1997. She is a graduate of
Connecticut College in Botany, a Connecticut Master Gardener and a national
award winning landscape designer for her landscape design and landscape installation work.
