Sweet chestnuts (Castanea sativa) are the fruit of the sweet chestnut tree which is in the Beech family. It is a true nut, a fertilised flower's ovary wall that swells and hardens, and has been cultivated for 4000 years, originally in the Mediterranean and Asia Minor. Enclosed in a very spiky case the nut is edible when raw but is more usually cooked, roasted, boiled, or dried to make a flour. Although it is most famous as a mid-winter treat it is important commercially in some areas and has several important health benefits but the harvest period is quite short and the nuts start to germinate shortly after falling so they must be harvested very quickly. As they do not have a long shelf life they have to be preserved in some way such as chestnut gluten free flour, a sweet spread (Creme de Marrons), and Marron Glaces, delicious regional specialities of France and Italy.