nidan verb (upper class) with 'hu/fu' ending (archaic), intransitive verb
Archaic intransitive verb for plants growing or springing up. In modern Japanese, 生える (はえる) is used instead.
In spring, grass grows.
The classical intransitive verb 生う meant “grow” or “spring up.” It belongs to the same historical word family as later 生える, but is a distinct older verb form.