Rubber mulches are often used in playground areas at schools, athletic fields, and parks. The sponginess of the rubber adds cushioning for falls. Crumb rubber is also sometimes used to artificially create more pore space in clay soils. Drawbacks of rubber mulch include the odor and, more importantly, the fact that rubber mulch does not break down over time as organic mulches do. When organic mulches break down, they add nutrients and structure to the soil. Because the rubber does not decompose, it would be hard to remove from the garden. That could be a problem if you need to replace any plants that die or redo the plantings.