To Bloom, To Blossom
intransitive verb, godan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means blossom or bloom and the verb version is to bloom.
さく
The reading is the same as the one you learned with the kanji.
この桃の木は、今までに一度も花が咲いた事がないんですよ。
This peach tree has never bloomed before.