In literature, and life, anything can be used as a symbol. A symbol is, essentially, the use of an image in order to represent something other than itself. Symbols are used to represent people, ideas, or beliefs (to name a few). Some symbols are used with the reader's knowledge in mind; other symbols are used in a more hidden way (as with allusions).
Symbols can be designed to be anything by the one constructing the symbolism. Sometimes, symbols are simply found by the engaged and critical reader.
As for the symbol of the pomegranate tree, it has been used throughout time. Many religions have used the pomegranate to symbolize beliefs and desires of mankind, birth and rebirth, marriage, prosperity, and abundance. The pomegranate's color, shape, and components of its makeup (skin, seeds, and juice) have all been used to symbolize different things.
Perhaps the one use of the pomegranate which has been used as a symbol, and forgotten, is the "fact" that it was not an apple in the Garden of Eden; instead, it was a pomegranate. This is a curious given the overly used symbol of the apple being a symbol of sin and not the pomegranate and the pomegranate tree (which would make the pomegranate tree the Tree of Knowledge).
This is an interesting question indeed. Pomegranate a symbol? the answer is definetely yes. The fruit/tree is considered as a greater symbolism in varied countries and religions though they circle the same thing i.e., the richness, fertility...
Many considered pomegranate as a symbol of fertility, fruitfulness and productiveness. Considering the ancient Egyptians, they regarded pomegranate as a symbol of prosperity and ambition. Pomegranates in Christianity acts as a symbol of the fullness of Jesus’ suffering and resurrection and in Islam it grows in the gardens of Paradise. Even in Hinduism they are associated with Bhoomadevi (mother earth) and Lord Ganesha. The Greeks name them as “the fruit of the dead” and it also represents life, regeneration and death for them. Further it is considered as a sanctity for its medicinal purposes in ancient countries like India.