Preferred bonsai soil types

The best bonsai soils should both retain water and let excess water drain through it. Additionally, it should resist compacting. This will allow it to stay aerated which will keep the roots healthier.

Inorganic Soils

Inorganic soils are preferred because they have all these qualities. Considered the best in this category, akadama soil, baked clay, is imported from Japan and can be found at certain bonsai suppliers. That is not to say it is your only option. Other types of fired clay soils may work, but akadama is considered the standard. Some people even use clay kitty litter.