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Akadamatsuchi (赤玉土, red ball earth) is a type of soil that is used for bonsai trees and other container-grown plants. It is a granular clay-like mineral that is mined from volcanic ash deposits in Japan, mainly in the Kanto region . Akadamatsuchi has different grades and sizes, depending on the depth and quality of the mining. The deeper-mined grade is harder and more suitable for horticulture than the softer, shallow-mined grade . Akadamatsuchi can be used alone or mixed with other materials such as sand, bark, peat, or lava rock to create a suitable growing medium for different plants . Akadamatsuchi has a pH of 6.9. It can retain water and nutrients while providing porosity and drainage for the roots of the plants . Akadamatsuchi is also valued for its color change when moist, which can help the grower determine when to water the plants.

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