Lesson 6.2 Other Growing Media
Completion requirements
Section 6: Soil, Other Growing Media, and Fertilizer
Lesson 2: Other Growing Media
During the summer months, nothing looks nicer than hanging flower baskets or overflowing floral window boxes.
Gardeners also like to bring potted plants into the home to add touches of green to inside spaces all year round.
But such "container gardening" requires special growing media, since the containers are too small and shallow for soil to adequately provide water and nutrients for a plant, and yet drain well enough to help plants thrive.
Hence, special potting soils are used. Such potting mixes are sometimes referred to as soilless, meaning they do not contain the type of dirt you would find in your yard or garden.
However, sand is sometimes added to them, especially for cactus and other succulent plants, to provide for superior drainage. But this adds extra weight to the mix, which makes it less suitable for balconies and/or hanging plants.
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The main ingredients in potting soils, are:
Also called peat, it holds water. Peat moss is a very stable source of organic material that holds a great deal of water and air, and does not decompose quickly. It is quite acidic, so that limestone is sometimes used along with it
to neutralize the acidity. Peat moss is the most widely used soilless growing medium, because of its wide availability and relatively low cost.
Perlite is a volcanic rock that has been heated and expanded to become a lightweight, white material. Added to a soil mix, perlite can improve air space and water drainage. It is a hard material that does not break apart, and it will hold
from three to four times its weight in water, yet will not become soggy.
Vermiculite is also a volcanic product. It has the excellent property of improving soil aeration while retaining the moisture and nutrients necessary to feed roots, cuttings, and seeds for faster growth. Like perlite, vermiculite will not
deteriorate, turn moldy, or rot, but it is not as acidic as perlite. Vermiculite is very light and easy to handle, and it mixes easily with soil, peat, and composted organic materials.
Coarse sand is sometimes used in place of perlite or vermiculite. Sand does not retain water and is thus more suitable for succulent plants. It is much heavier than perlite or vermiculite, and the added weight is good for tall, top-heavy
plants that might blow or tip over. Sand is the least expensive and the most readily available source of larger-particle material.
Compost products are made from a variety of locally available materials high in nitrogen and high in carbon. Compost holds water well and provides nutrients. It can be used with peat moss, or in place of it. Compost is cheaper than peat
moss and contains nutrients.
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Water as a Growing Medium
Water is also an alternative medium for growing plants. Hydroponics consists of having the roots of a plant suspended in water. Sometimes, perlite soaked in water is used. Soil is not used.
Plant nutrients (fertilizers) are dissolved in a continuous flow of water. The nutrient solution must be carefully monitored for appropriate concentration levels.