The makrut lime (Citrus hystrix), also known as the Thai lime or kaffir lime, is a citrus tree producing uncommon fruit. These remarkable limes are round in form and covered in a green, wrinkled, bumpy rind unlike that of any other citrus. While other citrus fruits are prized for their juicy flesh, makrut limes are loved for their strange peels, which are widely employed in southeastern Asian cuisine. The fruit itself is overly sour and bitter.
The makrut lime is a small tree, attaining a mature height of just 6 to 35 feet. Its Latin species name "hystrix" means "hedgehog," a reference to this plant's intensely thorny nature. Its twiggy, thorny branches are dark green and leathery in texture when young, darkening to brown with maturity. Its leaves are deeply lobed in the center, giving them the appearance of two regular lime leaves attached at the tips. For this reason, the makrut lime is alternately known as the double leaf lime or the two leaf lime. Its flowers are fragrant, with four to five small white petals tinged with yellow and violet hues. The leaves, bark and fruit peels are all high in aromatic, volatile oils, causing them to emit a fresh, spicy aroma when crushed or bruised.
Native to Thailand, Indonesia, Laos, Sri Lanka and the Philippines, the makrut lime tree thrives in moist tropical or subtropical conditions. In colder climates, it may be grown in large, portable containers able to be brought indoors in winter. Frost can prove deadly to this tree. Light, deep, well-drained soil is preferable, as is full sun. Makrut lime is a surface-rooting tree, and as such benefits greatly from a thick layer of mulch applied at the base of the trunk. This keeps its sensitive roots from drying out and keeps soil moisture even. In dry weather, a deep, thorough watering daily is recommended. Dead wood and leaves may be pruned away as needed.
Both the fresh grated peel and the leaves of the makrut lime are essential to Thai cooking. The leaves may be dried but are much more flavorful when used fresh. These leaves add a fresh, lemony flavor to soups, fish patties and curry dishes. They are frequently used in tom kha gai, or coconut soup, as well as tom yung goong, or hot and sour soup. Makrut lime leaves are frequently used in association with lemongrass, galagal, chili peppers, coconut and fish sauce to create authentic Thai flavors.
Medicinal and Other Uses
The acidic juice of the makrut lime is used in Asia as a bleaching agent for laundry, a cleansing shampoo ingredient and a room deodorizer. This juice has also been applied externally to skin to combat eczema. The purgative properties of the plant are employed in traditional southeastern Asian medicine to treat the symptoms of hepatitis. On the island of Reunion, a decoction of makrut lime roots is concocted for the purpose of relieving stomach pains, fevers, colds and hypertension.