Mulch also prevents weeds, holds moisture, and in most cases, adds organic matter to the soil.
Some mills also add some ground wood or sawdust to the mix.
The longer shredded bark remains in a stockpile, the darker it becomes. If bark remains in a stockpile too long, anaerobic conditions within the pile can allow toxins to build up. If used too soon, the fumes from this mulch will kill annual flowers as well as burn your shrubs and bordering lawn. Some people feel that watering this mulch right after it is spread will reduce the chances of damage. It is an excellent mulch for flower beds and as a replacement for straw on new lawns.