This paper examines the unidentified tree species "X" mentioned in the Sakuteiki, the oldest known Japanese garden treatise, compiled in the late Heian to early Kamakura period. The character "X" appears in a passage that describes the ideal placement of trees to create a "Shijin Sōō" (four guardian spirits) landscape composition, specifically recommending three plantings to the north of a residence when a hill is absent. Traditionally, "X" has been interpreted as hinoki (Japanese cypress), natsume (jujube), or nire (elm), but no consensus has been reached. Through a comparative analysis of various Sakuteiki manuscripts and reference to Chinese texts such as the Zhai Jing (宅経) and Qimin Yaoshu (齊民要術), this study finds that the character most plausibly represents nire. The manuscript evidence shows that the written form of "X" closely resembles the character for nire or possibly natsume, while literary sources consistently associate nire with northern planting in geomantic practices. These findings suggest that the Sakuteiki’s description of "X" reflects not merely textual borrowing, but also a deeper alignment with continental landscape thought. This study contributes to our understanding of plant symbolism and Chinese influence in early Japanese garden design.
A. Sato (Wed,) studied this question.