The common name for the orange fruit used in marmalade is the Seville orange, also known as bitter orange. These oranges are known for their tart taste and thick skin, making them ideal for marmalade production. Seville oranges are typically harvested in late winter to early spring and are favored because their bitterness balances well with sugar, resulting in a flavorful preserve. Marmalade has a long history, especially in British cuisines, where it’s often enjoyed on toast during breakfast or as a filling in pastries, showcasing the versatility and culinary significance of this citrus fruit.