A flowerpot filled with potting soil
Potting soil is a mixture used to grow plants, herbs and vegetables in a contained garden environment. The first recorded use of the term is from an 1861 issue of the American Agriculturist.[1]
The most common ingredients used in potting soil are peat moss, composted bark and/or other plant materials, sand, and perlite (for drainage). Some potting soil mixtures contain particles of vermicompost, while other contain vermiculite for water retention. Most commercially available brands of potting soil have their pH fine-tuned with ground limestone, and some contain small amounts of fertilizer and slow-release nutrients.[2] Despite its name, little or no soil is used in potting soil because it is considered too heavy for growing houseplants.[3]
Some plants require potting soil that are specific for their environment. For example, an African violet would grow better in potting soil containing extra peat moss while a cactus would thrive in potting soil that contains extra sand.[4] But potting soil is not ideal for all contained gardening. Insectivorous plants, such as the Venus flytrap and the pitcher plant, prefer nutrient-poor soils common to bogs and fens[5] while water-based plants thrive in a heavier topsoil mix.[6]
Commercially available potting soil is sterilized, in order to avoid the spread of weeds and plant-borne diseases. It is possible to reuse commercial potting soil, provided that the remnants of plant roots, fungus, weeds and insects are removed from the mixture through heating before new planting can take place.[7] Packaged potting soil is sold in bags ranging from 5 to 50 pounds (2.3–23 kg).[8]
As with garden soil, potting soil can attract insects. For example, the fungus gnat is often found around houseplants because it lays eggs in moist potting soil.[9]
On June 13, 2000 the U.S. Centers for Disease Control (CDC) reported that a woman in Washington was hospitalized with pneumonia that was triggered by Legionella longbeachae, the virus associated with Legionnaires' Disease. The CDC also confirmed cases of Legionella longbeachae infections from potting soil in Australia and Japan.[10]
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