Espoma Organic Bonsai Mix is an all-natural organic blend of the finest natural ingredients including calcined clay and expanded shale. Designed for optimum support, aeration, drainage, and improved moisture retention. This mix was specially formulated for use with all Bonsai to help roots grow and the plants to thrive. When repotting Bonsai, Spring is the best time to repot. Add a layer of this mix to the bottom of the container, and place the trimmed Bonsai in the container to inspect for height and growth orientation. If necessary, add more mix to raise plant height in the container. With orientation set add the mix around the roots to fully fill the container. Press mix down with fingers and planting stick to eliminate air pockets. Ready-to-Use.