What season are two orioles singing green willows?

Spring. Two orioles singing among the green willows is a poem written by Du Fu, a poet in the Tang Dynasty, which means that two orioles are singing gently among the green willows. In China culture, oriole is one of the symbols of spring, because oriole will start singing in spring, while willow trees mainly grow and bloom in spring. This sentence describes the scenery in early spring, so two orioles are singing green willows.