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 are somewhat harder and more useful in horticulture than the more softer, 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 color darkens when moist which can help the grower determine when to water a tree.