Each season offers a chance to improve garden tilth and plant food content.
R. Milton Carleton
Vegetables for Today’s Gardens
Vegetables are valuable for their content of vitamins, minerals, and fiber. How well do these important components hold up in storage?
The vitamin A content of squash (and presumably pumpkin) actually increases during storage. The variety grown and the conditions during storage determine the amount of the increase, so no exact figures can be given.
B vitamins are apparently quite stable in storage. Losses are usually small or negligible. Growing conditions can affect the content of certain B vitamins, though. For example, some studies have shown that application of trace minerals to the growing plant increases both thiamine and riboflavin content of the food. And in another study, turnips harvested in the morning contained more riboflavin than those harvested later.
Fiber and mineral content remain essentially unchanged in sound vegetables. Some vegetables become more fibrous as they age.
When green vegetables wilt, they lose vitamin C content. Well-fertilized kale, cabbage, and collards contain more vitamin C than those grown in low-nitrogen soil.