Both the kaffir lime (species Citrus Hystrix) and the key lime (species Citrus Aurantifolia) originated in Southeast Asia and are now worlds apart. The kaffir lime is still used mainly in Southeast Asian cooking. Because the fruit has such a high acidity, it is mainly the leaves of the Citrus Hystrix and the zest of the rind that are used for cooking.
The juice of the fruit and the rind are used for medicinal purposes in Indonesia. Extracted oil from the rind is used as a strong insecticide. In Thailand, the juice of the kaffir lime, though not considered suitable for cooking, is used as a cleaning agent. The plant is now grown around the world as a decorative garden bush, mainly because of the unique 2 part shape of the leaves.
Key Lime Facts and Uses
Key lime is actively cultivated for the fruit in the United States, Central America and Mexico. The name was attached to the Citrus Aurantifolia because it was used as a flavoring in the popular Key Lime Pie from the Florida Keys. The fruit is aromatic and also has a very high acid content, which gives it a very unique tart, almost bitter flavor.
For the Citrus Hystrix, the leaves are used as flavoring more than the fruit, but the Citrus Aurantifolia is grown for the special flavor of the fruit. Both are grown on trees that are used for their decorative properties and appear in gardens and backyards around the world.