This research aims to examine the types and characteristics of plant materials used in ancient rampart construction techniques and their implications. For this, it analyzes the plant remains excavated from the west rampart of Wolseong and the east rampart of Seongsan Sanseong. The results of the analysis demonstrate some common characteristics of plant materials found in the base of the ramparts at both sites. In the case of Wolseong, plant
wastes such as husk, rice straw, wood processing residues, charcoal, and various seeds and fruits form the majority of materials alongside some pottery fragments and animal bones. It is assumed that these materials, also found in the base of Seongsan Sanseong s east ramparts, were the by-products of various daily activities. For the technique of stacking up the main body of Wolseong s west rampart, crop by-products, such as rice straws and other Poaceae stems and leaves, were used. Rice straws are presumed to have contributed to the stability of the earthen walls due to their high concentration of silica, which made them excellent construction material with high water absorptivity and hardness. The “leaf mat method” has been used as a broad term referring to the use of plant materials for reinforcing earthen structures. This study suggests that the two distinctive processes which fall under this broad term should be distinguished. One is the “filling process” in which a large amount of miscellaneous plant debris from daily lives are stacked up. Another is the “laying process” in which selected substances, such as branches and herbaceous materials, are placed in between soil layers. In relation to the preceding research, this study suggests the possibility that, despite the rubbish-like appearance of the artifacts and ecofacts discovered from the doorway of the rampart, they may have been the remains of a foundation ritual.