Mulch is comprised of organic materials (grass, leaves, etc) and shredded wood. It protects your garden from weeds and as it breaks down over time, it fertilizes your garden.
How do they make black mulch?
Black mulch is simply brown mulch that is sprayed with black dye. Depending who you talk to, the dye may or may not be good for your plants. What is known is it will stain your driveway but in the right area does a great job of adding curb appeal.
Can mulch be bad?
The main disadvantage of mulching is that it can create a hiding place for harmful insects, and when applied too thickly can suffocate your plants by overheating the soil and starving them of light and water.