Topsoil is one of the haziest terms used by gardeners, and by those who sell the stuff.
After all, it’s nothing more than the top layer of soil. But real topsoil also is the most fertile portion of soil, formed in forests as autumns leaves are digested by soil life, releasing nutrients and creating humus. In the meadows the remains of old roots, leaves, and stems of flowers and grasses decay to create a potent mix on which new plants thrive.

No wonder the feeder roots of all plants – from magnificent maples to midget marigolds – choose to live and work in the topsoil. Here is where roots find a soft bed and a congenial mix of food, water and air.

Real topsoil, which takes centuries, even millennia, to develop, is a limited resource and is not what you necessarily get when you purchase “topsoil.”

That topsoil might be whatever soil happened to be in the upper layer of any piece of ground, which could be what was left after the real topsoil was eroded or stripped away.

Or, purchased topsoil might be made by mixing almost any soil with some organic material such as compost or leaf mold, actually creating a good substitute for the real thing.

Because topsoil is so ill-defined, ask questions before you buy it. Ask whether the topsoil was mined or made. Ask how much organic matter the topsoil contains. A rich, natural topsoil has about 5 percent organic matter.

Ask whether the soil is a clay, sand, or loam. For most purposes, loams are ideal. Clays tend to stay too wet and sands tend to be too dry.
Also ask yourself a question: Why are you buying topsoil? If you’re buying it to enrich poor soil in your vegetable or flower garden, don’t. Use homemade or purchased compost instead.

source : www.thevictoriaadvocate.com BY LEE REICH – THE ASSOCIATED PRESS