Aged pine bark is the one of the most common organic substrate components in the US, with bark from loblolly and longleaf pines being the most prominent in the southern U.S.  Aging is a modified composting process (no nitrogen source added) in which the bark is piled on the ground in windrows and allowed to age for a period of time, usually six months to one year. Aging time can vary between suppliers, or even for the same supplier, based on factors such as space shortages, product demand, or preference. The resulting end-products from these various procedures are all sold to the consumer as the same product, but are completely different in terms of percent fines, water holding capacity, air space, and nutrient immobilization, which will cause them to act differently when used in a growing mix. Fresh bark (bark that is sold shortly after removal from a tree, then ground, and screened to an appropriate particle size), may also be sold as a growing mix, and is preferred by some growers. Continue reading →