There is a deep brooding
In Arkansas.
Old crimes like moss pend
From poplar trees.
The sullen earth
Is too much too
Red for comfort.
Mosses are small flowerless plants that usually grow in dense green clumps or mats, in damp or shady locations. 
 The author uses nature as a symbol. For instance, she uses the moss to describe the “old crimes” of Arkansas, almost graffitiing the poplar trees. 

My Arkansas