Comparison of Root Ball Strength ofPaper Pot-and Container-grown Sugi Cuttings. J Jpn For Soc 105: 11-15 We conducted dropping experiments of the root ball of sugi (Cryptomeria japonica D. Don) cuttings grown in paper pots in order to compare the destructive strength of root balls with those of container-grown root balls reported in a previous study. Only small amount of soil medium was detached from paper pot-grown root ball in most droppings in spite of similar or lower root coverage of root ball surface (CRBS) compared to containerized root ball. Generalized linear models performed also demonstrated less soil detachment of paper pot-grown root balls than containerized root-balls under various CRBS and water content, indicating high effectiveness of paper pot in protecting the root balls of cuttings.