Pine bark is a byproduct of the forest industry. It comes in various sizes. It typically has a dark brown color.
Pine Bark Mulch or nuggets last longer than shredded wood mulch, but are not ideal for areas prone to flooding or heavy rains, as the bark chunks can float away. The bark pieces assist with retaining moisture. They also block sunlight from reaching weed shoots trying to sprout throughout the season.
PROS: sustainable; decomposes very slowly.
CONS: may float or wash away during heavy rains.