There’s no match for the flavor of a vegetable picked one minute and cooked the next. Once a vegetable is harvested it begins to change, and that change is almost always for the worse. (Exceptions include plant parts designed to hibernate, for example onions and potatoes.) Plant cells are hardier than animal cells, and may survive for weeks or even months. But cut off from their source of renovating nutrients, they consume themselves and accumulate waste products, and their flavor and texture suffer. Many varieties of corn and peas lose half their sugar in a few hours at room temperature, either by converting it to starch or using it for energy to stay alive. Bean pods, asparagus, and broccoli begin to use their sugar to make tough lignified fibers. As crisp, crunchy lettuce and celery use up their water, their cells lose turgor pressure and they become limp and chewy.