Black Plastic Under Rock Problems

Q. I’ve read somewhere that you should not place black plastic under rock used for desert landscaping. I have it there. We are an older couple and cannot remove it easily. Can we do anything else?

Black plastic under rock mulch tears and deteriorates in a few years. Shouldn't be used under rock.

A. I realize you understand that using black plastic is not a good idea under the rock. Using plastic under rock mulch in desert landscapes prevents air from reaching the roots. Roots need water, but they also need to “breathe”. Black plastic is not permanent while rock is. Sooner or later, this black plastic will begin poking through the rock mulch as it is punctured and disintegrates.

            Consider punching air holes through the plastic at the base of trees and other plants to help air reach the roots. The downside of this recommendation is it may cause the black plastic to rip and disintegrates sooner, peaking its ugly head through the rock.

            Don't think you have to remove all this plastic at once. If you see some sticking up through the rocks, remove it until more appears.

            A more expensive option instead of plastic is called a “weed barrier”. This is spun or woven material that “breathes”, allowing air and water movement. I personally don’t particularly like weed barriers because they do not prevent many of our most troubling weeds like common Bermudagrass and nutgrass. Instead I would recommend spending a little bit more money on rock mulch and applying it thicker, perhaps 3 – 4 inches deep instead of two.