For it seems that without the cuckoo's urging, the rhododendron cannot flower: And the origin of the flower's Chinese name, at least according to the Qing-dynasty travelogue Nan Yue Biji (Notes on Annam), is that "the cuckoo flower opens when the cuckoo sings."
沒有杜鵑聲催，杜鵑花更是開不了。甚至杜鵑花名的由來，根據清朝《南越筆記》記載，「杜鵑花以杜鵑啼時開，故名。」