What poem or verse contains the words and all the sumac on the hill have turned from green to red?

It is Indian Summer by William Wilfred Campbell.

Along the line of smoky hills
The crimson forest stands,
And all the day the blue-jay calls
Throughout the autumn lands.

Now by the brook the maple leans
With all his glory spread,
And all the sumachs on the hills
Have turned their green to red.

Now by great marshes wrapt in mist,
Or past some river's mouth,
Throughout the long, still autumn day
Wild birds are flying south.