Akadama (赤玉土, akadamatsuchi, red ball earth) is a naturally occurring, granular clay-like mineral used as soil for bonsai trees and other container-grown plants. It is surface-mined, immediately sifted and bagged, and supplied in various grades: the deeper-mined grade being somewhat harder and more useful in horticulture than the more shallow-mined grades. Akadama may also act as one component of growing medium when combined with other elements such as sand, composted bark, peat, or crushed lava. The colour darkens when moist which can help the grower determine when to water a tree.