Containerized planting stock is classified by the type and size of container used. A great variety of containers has been used, with various degrees of success. Some containers are designed to be planted with the tree e.g., the tar paper pot, the Alberta peat sausage, the Walters square bullet, and paper pot systems, are filled with rooting medium and planted with the tree (Tinus and McDonald 1979). Also planted with the tree are other containers that are not filled with rooting medium, but in which the container is a molded block of growing medium, as with Polyloam, Tree Start, and BR-8 Blocks.