Flower is one of the common images in ancient poetry. How to understand the sentence where petals flow like tears?

From Du Fu's "Spring Watch" in the Tang Dynasty, where the petals have been like tears, and the lonely bird has sung grief. These two sentences are mutual sentences, flowers are also sad for the country, tears are hard to stop, and the separation of relatives is shocking, which only increases hatred; Flowers shed tears, birds are shocked by the sadness of parting in troubled times. These two sentences personify flowers and birds with things, and feel the division of the country and the difficulty of state affairs. The flowers and birds in Chang 'an are all shocked by tears. Write about spring with flowers and birds, hurt things, and express the sadness of national subjugation and parting with personification. Reflect the poet's patriotic feelings. The author touched the scene, empathized with it, and saw the richness of good poetry.

Chang' an fell, the country was broken, and only the mountains and rivers remained; Spring has come, and the sparsely populated Chang' an city is densely forested. Sad state, can not help but burst into tears, amazing birds, leaving sorrow and hate.

The war lasted for more than half a year, and letters from home were rare, with a hundred thousand gold. Twisting with melancholy, scratching my head and thinking, the more I scratch my white hair, I can hardly insert a hairpin.

The capital has been breached, leaving only mountains and rivers. Chang 'an in spring is desolate and overgrown with vegetation. Flowers are also sad for the state, but tears can't stop splashing. Birds separated from their relatives are shocking and hate each other. The war has been going on for several months. Letters from home are precious, and a letter is rare enough to be worth tens of thousands of gold. Worried about white hair, the more you scratch it, the thinner it becomes, so little that you can't even insert the hair clasp.