If we think about seeds for one moment, they clearly represent growth and potential. Therefore, it is particularly relevant that Willy spends so much of his spare time working with seeds. Through such activity, we can see that he uses them to try and show the value of his work as both a family man and in professional terms. The way that he tries to cultivate vegetables at night clearly represents the embarrassment he feels and not being able to feed his family and not being able to provide for them, both in the present and the future. Above all, we can see that Willy feels leaving a similar legacy of lack of provision for his children as his own father left for him.
However, the occurrence of seeds in the play also point towards another metaphorical use of seeds to point towards child rearing. Willy's unshakeable belief in the American Dream has led him to follow its doctrines in raising Biff. However, clearly, the adult Biff is not the kind of person that Willy expected him to be having raised him to seize every opportunity for success. This is most strongly shown when Willy discovers that Bernard, Biff's weedy and weak childhood friend, has achieved the massive success he had desired for his own son. Willy is forced to realise that his hopes of raising a football hero have resulted in nothing more than creating a male who is unable to succeed in life in the way that his father had hoped.
Seeds therefore symbolically seem to taunt Willy with the various phantoms of failure that continue to haunt him in spite of his every deluded effort to ignore the evidence pointing against him.
The woods in Death of a Salesman symbolizes the the family's disconnection from nature. Although Willy continually impresses on Biff that he needs to get a more successful job, meaning in the city, Willy also speaks idealistically about the woods ie nature.
The jungle symbolizes adventure and boldness. These are also qualities Ben characterizes. Willy romanticizes his brother's success. The diamond ties into this idealistic success story as well since it is in the jungle that Ben finds the diamonds. Willy wishes that he had experienced this kind of adventure and success but instead he took the steady and predictable route.
The garden and the seeds represent Willy's desire to start over. He has worked as a salesman for many, many years, but he really hasn't necessarily enjoyed this line of work. He longs for a deeper connection with nature. He dreams of his gardens and he saves the seeds hoping to someday have this little piece of nature in his life as he grows older.
Seeds represent growth and maturity into a young flower. Willy always wants to plants seed but the seeds also represent how he wanted to plant Biff to be a great football star and become famous when in fact Biff did not grow at all. Willy kept on pushing and trying to instill his hopes into Biff but unlike the plants Willy was trying to grow, Biff did not grow at all and this partially mocks him.