A bonsai is confined to a relatively small quantity of soil throughout the on which its very existence depends. Through the soil in the post, the tree must be able to obtain water, nutrients and gases in order to grow. For this very reason, we have formulated Soil Mender Organic Bonsai Soil. Built on a base of all top quality, finished compost, we have added expanded shale and lava sand as well as other natural mediums for a complete soil.