How to Pick Potting Soil for a Container Vegetable Garden

Before you can start reaping the rewards of what pops above the surface in your container vegetable garden, some thought needs to be given to what lies below. Soil requirements for container-grown vegetables differ from those of the in-ground variety, mostly due to drainage and aeration. Thus, simply tossing some soil from your garden into pots will not do.

As a general rule, the growing medium in vegetable plants' containers needs to be looser and more porous than the material you would use in an in-ground garden. In a container, regular soil becomes too compacted and doesn't retain the water necessary for plants' roots. Commercial potting soils typically contain soil as well as porous rocks, which keep those potting soils looser than regular soil, and the porous rocks' holes store water.

If you buy potting soil from a garden supply store, look for a product that contains peat moss as well as porous rock such as perlite or vermiculite. Often, a potting soil mix also contains some garden soil, though ideally it is not more than one-third of the mix. If you want to make your own potting soil, then combine equal portions of peat moss, garden soil and either porous rock or coarse sand.

An all-purpose potting mixture can work well for most vegetable container gardening, though some vegetables tend to do better with a more specific drainage setup. If you will grow perennial vegetables, then use a potting mix that offers even more drainage. If, for example, you want a year-round crop of greens such as sorrel (Rumex acetosa), hardy from U.S. Department of Agriculture plant hardiness zones 3 through 7, or lovage (Levisticum officinale), hardy in USDA zones 5 through 9, then plant them in a soil mixture that contains two portions of vermiculite or perlite, one portion of soil and one portion of peat moss, or use a soilless mix.

Although soilless mixes can be beneficial for vegetable plants that need lots of drainage, take care which containers you use with them. Soilless mixes tend to be very light in weight, and as such, using plastic pots with them can result in tipped-over containers when the wind blows. Choose heavy ceramic pots for soilless mixes. Another option is to add clean sand to a container when filling it with a soilless mix, making the mixture about 10 percent clean sand. The additional weight from the sand can help keep the container upright during windstorms. Don't grow edible plants in a container that was used for a product that is toxic to humans or plants.