Question: Following your advice, I am planning to replace all of the stone mulch under and around the shrubs in my yard and use bark mulch, which attracts roaches, I am told.
Wood mulch attracts a number of animals and fosters plants that contribute to the breakdown of the mulch, and roaches contribute to that. These include mushrooms, earthworms and larvae of beetles, such as grubs and gnats. Mulches that decompose will attract decomposers.
Roaches tend to congregate in irrigation boxes in the landscape, and these should be treated periodically for control if this is a problem. I normally tell people to keep the wood mulch a couple of feet from the foundation of the house.
Rock mulch gives you a more sterile environment, and if thats what you prefer, then stick with it. Its best when used with plants that can tolerate it, such as most desert-dwelling plants. However, it adds nothing to the soil, and most plants perform better with wood mulch.
Bob Morris is an associate professor with the University of Nevada Cooperative Extension. He can be reached at email@example.com or 257-5555.