Gardening expanded clay
It is an aggregate with a porous structure characterized by high moisture absorption.
Sprinkled on the bottom of the pot, it is to create a reservoir of moisture and prevent the roots of the plant from constantly coming into contact with excess water. Performs the function of drainage.
Expanded clay is chemically neutral - it does not change the pH of the substrate, it is also resistant to any activity of mold or fungi, which reduces the risk of plant infection.