In the Thai kitchen, simply referencing the use of citrus leaves essentially means kaffir lime leaves. Kaffir plants are so common that the majority of rural households have their own kaffir lime trees to harvest from.
Kaffir limes are unique to common limes in their shape, texture, fragrance and flavor. Their appearance is memorably ovate with a rounded bottom and conical stem end. The peel is rough, pebbled and filled with essential oils that give the lime its trademark aroma. The juice of the flesh is extremely tart and often bitter, thus it is seldom used in cooking.
Kaffir limes are not true limes, though they are a member of the true citrus family, Rutaceae. Other common names for the Kaffir lime include combava, kieffer lime, limau purut, jeruk purut, Bai Ma-gkood or makrut lime.
The peel of the Kaffir lime is its indispensable culinary attribute. The leaves of the Kaffir lime tree are also used as an aromatic in cooking. The Kaffir lime’s intense, distinct fragrance cannot easily be substituted by other spices.
The Kaffir lime tree is native to landlocked Laos, Myanmar, Thailand and other parts of south Asia. The trees thrive in warm, humid climates and like other citrus varieties are extremely sensitive to cold and frost. The tree bears fruit in the winter months and flowers throughout the spring and summer.