I didn't know these flowers were blooming now. They smell so nice.
I didn't realize these flowers were in bloom at this time of year. What a nice smell!
この場合、次のような言い方ができますよ。
ーI didn't know these flowers were blooming now. They smell so nice.
「今この花が咲くんだ。いいかおり」
ーI didn't realize these flowers were in bloom at this time of year. What a nice smell!
「この花は今が時期なんだ。いい香り」
ご参考まで!