Usually yellow sand. What we usually call yellow sand contains two kinds of sand, one is river sand and the other is mountain sand. Taken from the river course and river bottom, it is collectively called river sand, and mountain sand is stone powder sand. Both kinds of sand can be used to cut or mix soil for planting. River sand and mountain sand can be obtained from the construction site, and residents can also decorate it. There are many fallen leaves under the big trees in the park every year. The decaying leaves in previous years were humus, such as rotten leaves of pine trees, also called pine needle soil. They are all good media for cultivating plant bonsai, generally mixed with yellow sand.