"Why are carrots harvested after winter particularly sweet?" Plants use sugar as an internal antifreeze. This is an example of the concept of freezing point depression. When a solution freezes, the molecules into a crystalline structure. However, when impurities are introduced to the solution, they block the molecules from clustering together and freezing. In the case of carrots, sugar is the impurity, and it keeps the liquid inside the plants from freezing at 0 °C. This defense mechanism against frost translates into carrots that taste extra sweet to us. Even on a daily basis, Barbara always picks her carrots and melons before the sun comes up, because sugar levels increase at night. Strawberries ripen at night, too.
Image courtesy of farmstayus.com Out where the farm is in Paso Robles, the valley makes for a very active microclimate. The difference between daily temperature highs and lows can be as large as 50 °F. Apples, which need a certain number of hours of frost, thrive well there. Storage is just as important as growth, and Barbara invested in a refrigerated truck for transporting vegetables. Leafy greens always need water, and this is why supermarkets and farmers are always spraying or misting. There is a rule of thumb that every hour lost in not cooling freshly picked vegetables to the proper temperature equals one less day of shelf life. We were surprised to learn about the storage capabilities of some apple varieties, such that you can keep them for months on end. They'll be good right after picking, become very gnarly quickly, and then, if you wait long enough, they'll taste fantastic again. Which varieties do you know are like that?