What is Growing Media?

The potting soil or garden soil that your plants grow in is called the “growing medium”.  Dozens of different ingredients are used in several combinations to create homemade or commercial potting mix. Ingredients such as: peat moss or clay soil. By understanding the functions of different types of potting soil, you can evaluate the qualities of individual types and select which ones might work best for your indoor garden or hydroponic system.

The choice is very important because your plants are dependent on a relatively small volume of potting soil. Unlike others growing in garden soil, containerized plant roots cannot grow around obstacles or mine the soil far and wide for nutrients and water.


Potting soil has three main functions:


  • Supply roots with plant nutrients, air, and water
  • Allow for maximum root growth
  • Physically support the plant.


Roots grow in the spaces between individual particles of garden soil.  Air and water also travel through these pore spaces.  Water is the medium that carries nutrients that plants need to fuel their growth, and air is needed for root growth and the health of soil microorganisms that help supply plants with nutrients.

Irrigation water moves through the pore spaces, pushing out the air.  If excess water cannot drain away, fresh air cannot enter and roots will suffocate, so select light and fluffy growing media for good aeration and root growth.