花开了用英语可以说成 "the flowers have bloomed"。这个短语表示花朵已经绽放，它有着明显的生物学意义，指植物的花朵已经从蕾朵变成完全绽放的状态。

例句：

The cherry blossoms have bloomed, it's a sign that spring has arrived.

(樱花已经绽放了，这是春天来临的标志。)

The roses have bloomed, their scent fills the air.

(玫瑰已经绽放了，它们的香味弥漫在空气中。)

The sunflowers have bloomed, they are now facing the sun.

(向日葵已经绽放了，它们现在面向太阳。)