Not sure which compost is best for your needs? Check out our guide to choosing the right compost for your flower or vegetable garden.Compost is decomposed organic matter that is rich in nutrients and often a course, dark brown, peat-like material. Adding compost to your soil improves the overall structure and texture. It increases the capacity to hold water in sandy soils, and enhances drainage in heavy clay soils. It also attracts earthworms that help aerate the soil and beneficial microbiology that helps convert material into molecules and elements that plants can more easily absorb.