Genesis 1:29

And God said, Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in the which is the fruit of a tree yielding seed; to you it shall be for meat.

1. God told the man and woman that he had given them the herbs and fruits of the trees for food.
2. God must have instructed the man and the woman before this point about the edible herbs and fruit so they would know which they were. Otherwise, they might have eaten poisonous ones, which would have ruined his plan.