Judy - Maybe in a wet environment yea, but I've been using mulch on my yard for the past .. hmm.. 8? years and never had a problem with standard mulch. I personally don't like bark mulch, to me, it's ugly. I have to spot mulch yearly and redo my entire yard every 3-5 years. I've found that my yard, being in a very dry, xeric environment, benefits GREATLY from heavy mulching.. when I first bought my property, I could grow tumbleweeds & pigweed & thistles and that was about it without having to water every single day. Now? I have over 300 rose bushes, shrubs, trees... and worms! Lots & lots of worms! I didn't have worm one when I first got my home in 2005. Personally I prefer cedar mulch as it lasts the longest, but it's also the most expensive ($41/cy not including delivery), so that's why I contact tree companies. Locally grown trees seem to work the best for ground cover.. plus you don't have to worry about funky dyes or pesticides or antifungals or whatever!