Some vegetables are best left in the garden and picked only as needed. Sweetcorn and peas should be popped into boiling water as soon as possible after harvesting as their sugars quickly turn to starch. Parsnips are best left in the ground throughout the winter so that the starch can be converted into sugars, which helps them roast. And cherry tomoatoes should be popped into your mouth as soon as they turn red, ideally on a warm summers evening!