you will find the beans seeds before you go up completly on Mt.Orion (before you kill the enemy) go to your left and you will find the house of Oghy (or something like that), search his house and there you will find it, you have to brings those seeds to the old lady that planted the offering to the gods, and she will planted for you, don't wait for it because it takes certain time for you to be able to pick it up