What does this poem mean? the literary techniques and the main idea?

“Fall, leaves, fall: die, flowers, away,” by Emily Jane Brontë





Fall, leaves, fall; die, flowers, away;


Lengthen night and shorten day;


Every leaf speaks bliss to me


Fluttering from the autumn tree.





I shall smile when wreaths of snow


Blossom where the rose should grow;


I shall sing when night's decay


Ushers in a drearier day.

What does this poem mean? the literary techniques and the main idea?
It's literary technique I would say is rhyming. It's talking about the end of Autumn is welcoming the new season of Winter.