Many symbols are incorporated into the play "Death of a Salesman", which are the basis of the motifs and themes that develop throughout the play. These symbols become part of the character and the motifs of the play.
One of the diction motifs that run in the play is life and death. As the play begins, we are introduced to the motif of death and the incapability of growing life in the back garden due to the realistic domination of materialism and the concrete walls that cast the shadow of death upon the plantations.
Towards then end of the play, and as Willy Lowman reaches the beginning of his end and of his downfall, he feels that he must leave something behind him, something that will live and outgrow him. The seeds are symbolic of the life continuing his; the life that he dreams of for Biff Lowman, his son, and the wants this imaginary life to consist of a magnificent Biff that resurrects the "American Dream" that Willy Lowman could not successfully achieve.
In spite of his action in planting the seeds, he is destined to fail just as he has failed in achieving every aspect of his "American Dream". He plants the seeds at night; however, there is no sunshine at night and this oddly raises a doubt to why he does so. Willy reached his downfall and his act of planting seeds at night shows us his desperate need to resurrect his dream in the eyes of his "American Dream Idle Son"
Another strange fact is that Willy is boxed between the concrete walls of Capitalism. His dreams are becoming part of these walls which hold the basis pillars of materialism; however, we see him contradicting himself trying to escape the walls...