Perlite, to mix with potting soil for better drainage and aeration
Perlite is a volcanic material that is heated whereupon it pops much like popcorn and expands to 13 times its former size, resulting in an incredibly lightweight natural material. The addition of perlite to potting soil helps with water drainage and better root development. Especially when you like to root cuttings.

The best ratio for sowing or propagation is 1 part Perlite to 3 or 4 parts potting soil. This will make your soil a lot lighter and airier. Perlite is RHP certified and allowed in organic farming!