Black rubber mulch is an inorganic mulch made from recycled tires. Rubber mulch is growing in popularity because it is inexpensive, considered an eco-friendly way to recycle tires and is very long-lasting. There are some cons of black rubber mulch, however, that should be carefully weighed before spreading it in your garden.
Some rubber mulches still have bits of steel belts imbedded in them. This can be dangerous when kneeling or digging. While most new rubber mulches for home gardens go through a process to magnetically remove these hazards, some commercial brands or older mulch still pose a threat.
Rubber mulch may contain chemicals and heavy metals that can leach into the ground. This can kill plants, poison ground water and nearby bodies of water from run-off, and turn fresh vegetables into a health hazard. Zinc is the biggest threat in rubber mulch, but other toxins such as arsenic, cadmium and lead have been present.
In regions where plants are in danger from summer heat damage, black rubber mulch can exacerbate the problem. It can absorb more heat under the hot sunlight than your plants can bare, even enough to bake your plants to death.
Rubber mulch can make the area around your garden smell of dirty rubber, at least after initially spreading it. Rubber mulch supporters claim this smell eventually fades, but it can be very unpleasant for a while.
Rubber mulch is very hard to get a shovel through, so when you need to change your landscaping by adding new plants or digging up old ones, it will have to be raked or swept aside. Bits of it can get into the soil, building up after a few years, making the soil more difficult to work in.
While it may be practical and convenient, some consider black rubber mulch unattractive. If the garden is in the front of your home, near a patio or lounging area, and it's purpose is to help the home's appearance, consider how your ornamental plants are going to look in a field of dull, black-shredded rubber.
Void of Nutrients
Black rubber mulch adds nothing to improve the quality of the soil. Organic mulches will break down and be an asset to the soil, replenishing nutrients and keeping it healthy. Black rubber mulch, even if it is toxin-free, is at best completely neutral. Your plants will not benefit from it.