Studies have found that crumb rubber can emit gases that.

Apr 25, Contains chemicals dangerous for plants. Rubber mulch includes chemicals which can be very harmful to the plants, and one of these chemicals is zinc (Zn). While zinc is naturally found in the soil, a high concentration of this chemical element can be harmful to the soil and plans. The majority of the rubber mulch we find is made from recycled bushfelling.clubted Reading Time: 6 mins. Rubber mulch rings are less effective than natural mulch and can possibly hurt your tree.
As the rubber breaks down over time, the rubber adds toxic contaminants into the soil. It's the mulch that's most likely to ignite and difficult to extinguish, according to Ohio State University research. Jun 27, Rubber mulch is commonly used, for safety reasons, in areas where children play. The idea is that kids will"bounce" off of it when they fall down, making it safer than other materials. It also boasts other good qualities, prompting a spread in its use from play areas to the wider landscape, including bushfelling.clubted Reading Time: 3 mins.
Sep 23, Impact on weeds – Rubber mulch is less effective in controlling weeds than organic mulches. Impact on Plants – Studies identified symptoms of leaf yellowing, reduced tree growth, and increased tree mortality. Plus, soil tests show high levels of zinc which can be toxic to plants and could cause leaf chlorosis.