In the East Gardens of the Imperial Palace in front of the Palaceside Building in Takebashi, Tokyo, pieris (asebi) and dawn pieris (akebono asebi) planted north of the spring in Honmaru Green are covered with many small flowers like lily-of-the-valley. White flowers are pieris; pink are dawn pieris—adding bright color to the still-sparse, lonely early spring.
Pieris, also written ashiwi, is written in kanji as 馬酔木 (horse-drunk tree). The leaves are poisonous; horses that eat them stagger as if drunk and suffer—that is said to be the origin of the name. Herbivores such as deer seem to know this and eat other leaves, so pieris alone often remains and stands out. The leaves were also boiled and used as insecticide.
Yet cafés, coffee shops, and restaurants named "Horse-Drunk Tree" can be found in many places. One might wonder why a dining establishment would deliberately take the name of a poisonous plant. Perhaps each small flower's delicacy and the splendor when they bloom in clusters inspired the choice.
In the Man'yōshū, author unknown, there is a waka:
Like the horse-drunk tree / you who flourished— / the stone well's water / from the well you dug: / could one ever tire of drinking it?
It praises a noble person and the well—meaning the stone well's water is so fine one could drink forever without growing weary. "Like the horse-drunk tree" is a pillow word for flourishing; the white flowers hanging downward are likened to rice, guaranteeing abundant grain and celebrating prosperity.
After Masaoka Shiki, the tanka magazine "Horse-Drunk Tree" was published by the Negishi Tanka Society devoted to sketch-from-life, with Itō Sachio and Nagatsuka Ippeki among the editors; there is also a "Horse-Drunk Tree" among the haiku magazines of Mizuhara Shūshi, Yamaguchi Seison, Ishida Hakyō, and others.
It was probably named not only for the flower's appearance but to share in the "flourishing" expressed in the Man'yōshū.