Hi,

Children return to their homes and spend time with their families. Now echoing green looks like a dark and gloomy in the evening. The joy of childhood contrasted with old age poet called it darkening green.

Blake started the poem with the mention of the rising sun, to denote the beginning of the day, or metaphorically, the beginning of life. The rising sun symbolizes childhood or youth, a time when everyone is happy and joyful.

In the last stanza, the mood is melancholic where the “Echoing” green becomes the “darkening” green. Spring will always come, but it will eventually end. This symbolises that joy and vitality of the season will give way to coldness and gloominess of autumn and winter.

When the sun sets, the fields become dark. The children stop playing and go to their mothers to rest. The birds also return to their nests.

Hope this helps

Wish you luck