Japanese dock; Rumex japonicus
A perennial weed of the buckwheat family, common in fields and roadsides in Japan. The name is often written in katakana.
A lot of Japanese dock is growing by the roadside.
Kanji form is rare and mainly used in botanical contexts; the reading ようてい is also possible but uncommon.
Hiragana variant, also used.
The name ギシギシ is likely mimetic, possibly from the rustling sound of the leaves or the plant's rough texture, but the exact origin is uncertain.