I wanted to see which medium was best for starting root growth and would grow quicker for starting seeds and germination. This is a comparison between Rockwool cubes, Hydroton Clay, Perlite, and Miracle Gro potting soil. Materials used in the experiment Miracle-Gro Moisture Control Potting Mix 1.5″ Rockwool Cubes Clay Pellets Dwarf Blue Kale Miracle-Gro …