54February 9, 2011

The conversation usually goes like this; “Hi, I’d like to buy a bag of dirt.” I’ve learned over the years to ask a few questions when a conversation like that happens in my store. The customer may be looking for a bag of topsoil or they may actually need a bag of potting soil. Some of you may not be sure when you should be using topsoil or when you should be using potting soil for a gardening project. Let me take a few minutes to clear up this question.

If you want a simple answer to this question then just remember the following lines. If you are planting in the ground, you can use topsoil. If you are planting in any type of container, then use potting soil. Topsoil, nowadays, is usually made of compost and other decayed organic matter. It is used to improve soil in the yard or garden. Because the soil is rich in organic matter, it will hold lots of water. The addition of topsoil to a sandy soil can greatly improve the moisture holding capacity of the soil as well as help to retain fertilizer in the soil. If you use topsoil in containers, that ability to hold moisture can actually be harmful to the plants being grown in a container. Topsoil will hold so much moisture that the roots of container grown plants can actually die from too much water in the soil.

Potting soil is usually a blend of ingredients. Topsoil is hardly ever used as an ingredient in a potting soil.  Along with its ability to hold too much water, topsoil can also contain fungus and bacteria that can be harmful to plants being grown in a container. Most potting soils are a blend of peat moss, perlite or vermiculite, ground bark and in some cases horticultural sand. This type of a mix allows for the absorption of water while allowing excess water to drain away. The peat moss helps to hold in the fertilizer that you should be adding to the soil on a regular schedule. Potting soil allows the roots of your plants to thrive.

Next time you are looking for soil for re-potting your houseplants or if you are filling window boxes or other planters this spring, make sure that you are using potting soil. If, after this winter, you need to fill in spots on your lawn that became a victim of a snowplow, you can use topsoil.

Well, that’s all for this week. I’ll talk to you again next week.

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