As mentioned above, it was often written in waka poems as a symbol of spring and pronoun for flower, and also in haiku world it has been used as a season word of spring from long ago.
上記のように春の象徴・花の代名詞として和歌によく歌われるほか、俳句の世界でも、古くから春の季語として桜が用いられてきた。