Adam and Eve were to eat of any of the trees of the garden except the one. They must have been fruit trees, since they were to eat of them. Eating (and drinking) in the Bible is figurative of partaking of a message. We can see that with meat, bread, honey, milk, water, wine, figs, etc. Therefore, a fruit tree would be a messenger. They were to eat of any of the messengers except the one in the midst of the garden.
It was Satan in the form of a serpent who wanted Adam and Eve to eat of the tree of knowledge of good and evil. It seems Satan was the messenger represented by that tree. His lies seemed good for food and Eve partook of the message and shared with Adam. Because they have accepted the error they are put out of the garden and now the fruit trees with the message of truth and life are as security guards and their message is as a flaming sword. They want to slay Adam and Eve with their message so they can get to the Tree of Life, but Adam and Eve are afraid to approach.
The same message can be as fruit if you go to the messenger to partake, or it can be as a flaming sword if the messenger needs to come after you with it and it is different than what you believe.
Now the fields bring forth thorns. When Paul had an abundance of revelations he said that the thorn was a messenger of Satan. Satan taught the lie, Adam partook of it, and now Adam's field (congregation) brings forth messengers of Satan. They are going to repeat the message that Satan shared with Adam. This seems to be an allegory showing how error entered the religious world. Through one man error entered the world. That one man represents teachers in general and the woman represents those receiving the message.