Potting media vary greatly in content and quality.
Container grown plants have a limited amount of space from which to obtain water and nutrients. (See References 1) Gardeners can choose from a variety of growing media, known as potting soils and potting mixes, to meet these particular needs. According to the Virginia Cooperative Extension, potting soils contain a mixture of solid materials, air and water that work together to provide a suitable growing environment. Does this Spark an idea?
Types
Container gardeners can choose from two types of potting media: potting soil and potting mix. Potting soil consists of varying amounts of organic solids such as shredded bark or peat moss. Potting mix consists of organic and inorganic matter such as sand, vermiculite and sometimes fertilizer. A gardener can prepare a mix by purchasing inorganic matter and adding it to potting soil.
Features
Manufacturers and gardeners use the term "potting soil" to describe a broad range of media, according to an article published by the Mohave County, Arizona, Cooperative Extension. A good potting mix for indoor plants contains peat moss, vermiculite and perlite. On potting media package labels, manufacturers must list ingredients in descending order of volume. (See References 2) Potting soil should be slightly acidic with pH levels between 5.0 and 6.5. (See References 4)
Function
Unlike a plant in a garden, a container grown plant's root system cannot obtain water, nutrients and air beyond the container wall. Potting soils and potting mixes must be able to retain water and nutrients for the plant and provide adequate air space for drainage. Organic matter such as peat moss absorbs and releases nutrients, while inorganic materials such as perlite and vermiculite provide air and drainage space. See References 2)
Benefits
Potting soils and mixes are specifically designed to provide a suitable growing environment for container grown plants. Soil-less potting mixes are usually sterile and free of weed seeds, pests and diseases. According to the Iowa State University Extension, potting mixes tend to weigh less than potting soils, allowing a gardener to easily move the container. (See References 3)
Considerations
Manufacturers are not required to include particular ingredients in their potting mixes. In a study published in 1986, researchers at the University of California, Davis found that potting media package labels do not provide adequate information on the product's performance. (See References 4) According to the Virginia Cooperative Extension, mixes that contain garden soil or loam vary greatly in quality and can become too compact in the container. The addition of sand can also impair drainage.
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