Seville oranges have a very brief winter season from December to February. Seville oranges are a variety of sour oranges that are most commonly used for orange marmalade.
Seville oranges taste sour, tart and sometimes bitter. When the bitter flavor of Seville oranges is combined with sugar, the predominant flavor is oranges with a sharp, tangy taste. The bitterness of the Seville oranges eliminates the over-sweetness of most fruit preserves and contributes to an intensity of flavor in the marmalade. Seville oranges can be refrigerated for up to two weeks or frozen. Seville orange plants are used more as a rootstock for other types of citrus than for cultivating its own fruits.