What is vermiculite?
Vermiculite is made from a naturally occurring, non-toxic,
soft mica mineral. It is heated to a high temperature to produce a
lightweight, sterile, laminated structure, which ensures adequate soil
aeration while at the same time having the ability to hold moisture and
nutrients.
I have had good results using vermiculite, but this does not mean that is
absolutely necessary. Don't worry if you can't get hold of any, but keep
an eye out, and ask at garden centres if you can.