There are many benefits to adding organic mulch like shredded wood, wood chips and nuggets in the home landscape. Mulch helps retain moisture, helps prevent some erosion, reduces weeds and the spread of some diseases like leaf blight, and it looks good however, mulch can silently kill plants as well.
A problem with organic mulch is the depth. Most landscape information recommends between two-to-four inches of mulch.  Some homeowners unknowingly add inch after inch every year. The photo above shows approximately 17 inches of thick mulch around the base. Thick mulch can be a riskier problem than no mulch. Mulch that is too deep can harm or kill landscape plants including large trees, it can create havens for colonies of insects like carpenter ants and termites (in the south), and it's often an unnecessary waste of time and money.
A great solution to adding new mulch every year is to fluff the existing mulch. Fluffing mulch is also a good way to inspect for any critters and find hidden problems like girdling roots (choking roots that wrap around the soil surface). Typically, the original "fresh" color is hiding just below the surface as well which means you don't have to buy, haul, and handle new mulch!
1. University of Minnesota, Extension Office.