Coast of Maine Dark Harbor Blend Enriching Mulch is an exceptionally rich, naturally dark, fine-textured blend of self-composted barks. It is ideal for mulching beds, borders and gardens and for use around shrubs and trees. It also helps retain moisture, will not rob the soil of nitrogen (as raw barks will) and helps insulate the surface soil against excessive cold and heat that can damage plant root systems. Because the barks in Dark Harbor are fully composted, it can be dug into your beds in the fall, providing a rich and immediate source of organic material. It also acts as a long-term soil builder that supports microbial activity and opens up compacted soil.