“Topsoil” can refer to a wide variety of materials. The word has no legal definition. Before you buy, learn what you can about the history of the soil: where it came from, how it was processed, and what it may have been mixed with. Sometimes topsoil is sold mixed with various soil amendments, such as manure and ground bark.
Some “topsoil” is a blend of sand and organic matter, and not true soil at all. (This is not necessarily bad—some of the sand mixtures are excellent potting mixes and will grow plants quite well.)
Topsoil is usually purchased as a fill material, to fill a low spot or a raised planting bed. Sometimes it is purchased to solve a soil problem by just covering it over. Topsoil can also be used as a soil amendment, to be tilled into the native soil.
Here are some points to consider if you are buying topsoil:
- Visit the soil before it arrives at your door in a truck. See if it is free of rocks and debris and has a soft or crumbly structure. Try to match the texture of the soil in your yard; if you have sandy soil, buy a sandy topsoil. If you must buy soil of a different texture, till part of it into the surface of the native soil to make a transition zone and avoid a sharp change in texture. See Layered Soil for more information
- The topsoil should be free of weed seeds and toxins. If you have the time, grow a few radish seeds in a flat of the topsoil for 2 weeks. If the radishes grow well, there are no serious toxin problems. If weed seeds are present, the weeds will also show up within 2 weeks.