Simply stated, when organic material has been thoroughly decomposed and been through the appropriate number of composting cycles it becomes compost. More specifically, the composting process requires moisture, oxygen, aerobic microbes, carbon/nitrogen ratios and time. Compost is a nutrient rich material that feeds plants and creates an environment that is conducive to plant growth. It differs from mulch, as mulch (or partially decomposed matter) is typically non-decomposed material, and therefore harmful to plants if placed in the root zone (see our Common Problems page to view other common problems associated with so-called ‘compost’ that has not been fully decomposed).