I believe you get this together with Herb Cookies knowledge as well. Starting quest should be from chief of Florin (Valentine). Its a bit confusing, which one unlocks which knowledge.

要用莎亦以外的角色才能接任務!
弗洛林村長給的採花任務後續可以獲得，依序採花 -> 伐木 -> 採樹液後 -> 任務對話獲得。