dyer's knotweed; Persicaria tinctoria
A plant used to produce indigo dye. The name is usually written in katakana.
See also: 藍
Dyer's knotweed is cultivated as a raw material for indigo dyeing.
Usually written in katakana; usually written in kana.
Kanji form is rare; the plant name is normally written in kana.
The name likely derives from 藍 (あい, indigo) and 蓼 (たで, knotweed), referring to its use in indigo production. The exact historical derivation is uncertain.