The amount of vitamin C in foods of plant origin depends on the kind of plant , the kind of soil where it grew , how much rain and sun it got , the length of time since it was picked , and how it was stored since then . While plants are generally a good source of vitamin C , the amount in foods of plant origin depends on the precise variety of the plant , soil condition , climate where it grew , length of time since it was picked , storage conditions , and method of preparation .