The quality of your vegetables cannot be improved after harvest. It is therefore important to harvest your crops at the proper maturity. See Tips on Growing Specific Vegetables for information on harvesting specific crops.
To maintain quality after harvest, handle vegetables carefully. Avoid bruising or damaging them, for injury will encourage decay. Cool vegetables such as sweet corn, peas, asparagus, and leafy crops to below 40° F as soon as possible unless they are eaten immediately.