Olives, walnuts, almonds, and late developing fruit must all be brought in and preserved before the start of winter.
Olives that aren't brought in before the winter weather sets in will rot. 
mnli hypothesis: Olives that aren't brought in before the winter weather sets in will rot.  premise: Olives, walnuts, almonds, and late developing fruit must all be brought in and preserved before the start of winter.