Which materials are classified as nonorganic mulches?

Nonorganic mulches are materials that do not come from plant sources and do not decompose over time in the same way that organic materials do. Gravel and plastic sheeting fit this definition perfectly. Gravel, being a natural mineral material, provides excellent drainage and prevents weed growth without breaking down. Plastic sheeting, on the other hand, serves as a barrier against weeds and moisture loss, and it will not decompose, making it a long-lasting option for ground cover.

In contrast, the other options involve organic materials, which are derived from plant sources and will eventually break down. Bark and wood chips, for instance, are produced from trees and will decompose over time, thus falling under the category of organic mulch. Green or yard waste also consists of plant material that will decompose. Likewise, compost and lumber milling byproducts are organic as compost is made from decomposed organic matter, while milling byproducts are derived from wood, again making these options organic rather than nonorganic.