Hello Kathy,

Don’t do it!

There are several reasons why natural mulch is better than rubber mulch:

• While natural mulch decays and needs to be replenished, that decomposition is providing highly beneficial organic matter to the soil.
• Rubber mulch is generally ground automotive tires. They decompose too, but when they break down, they can leach petroleum oils, zinc and heavy metals into the soil. Also, any color rubber mulch (other than black) is dyed and when the dye washes off, the mulch looks blotchy.
• Rubber mulch also absorbs more solar energy than natural mulch, raising the soil temperature to an abnormal level.
• Rubber mulch allowed more weed growth than natural mulch in side-by-side tests.

Here are a couple of good references on the topic:

https://extension.illinois.edu/blogs/good-growing/2019-09-23-contaminated-landscape-materials-rubber-mulch

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/rubber-mulch.pdf