Mary - Huggable has it right as far as I'm aware. However you can never have more food than your max, so if you are already at your max you will not see the harvest option. If you are near your max you will see options to harvest up to your max. Also, after you seed and before you harvest you should weed. This is supposed to make your field grow faster. Lastly, your granary doesn't last forever. My first one just got too old to produce a few days ago. I think it lasted somewhere between two and three weeks, but I don't know how it actually ages, calendar days or how by often you play.