Have you read the whole poem?
Here it is.... in facsimile... from https://en.wikipedia.org/wiki/To_Autumn
You can read the whole thing if you go to the Wikipedia page. And the meaning, themes, structure, and everything else.
There's nothing "fruitful" left in our garden. This year our harvest was mainly apples (now in the freezer) and chillis.
"Where are the songs of Spring? Ay, where are they?
No, think not of the songs of Spring. It's going to be Christmas Carols for the rest of the year.