In the formal language of economics, X and Y are substitutes if the demand for X increases when the price of Y increases, or a positive cross elasticity of demand.
Potting mix is the material that goes into a garden pot before you put seeds and plants into it. 1  It keeps the plant in place. 2  It holds water for the plantâs roots to soak up.  It contains nutrients that feed the plant.
variations in the quantity potting soil s key ingredients sphagnum peat moss vermiculite or perlite and aged compost products determine the different types tip 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