The apocalypse comes, and it's even worse than a lot of people are expecting because, hey, in the real world all of the fruit and vegetable plants they sell (including, or perhaps especially, those sold to commercial farmers) are designed to be sterile--as in, after the crop that's currently in the ground gets harvested, if there isn't any more seed to be bought then we're not going to have anything to live off of other than domestic animals and whatever we can find out in the wild.