They
include all such materials that are used in the
professional and hobby markets, whether produced
by the growing media industry or by growers as
own-mixes. Media for all types of plant cultivation,
usually in containers, are included; as well as
fertilised planting media e.g. for trees and shrubs,
and casing soil for mushrooms. “Substrate” is often
used as a synonym for “growing medium” but its
definition is not so precise.