Kaffir lime trees (Citrus hystrix) are small citrus trees native to Indonesia. The leaves of the tree, which have a slight, lemony flavor, are used in many southeastern Asian recipes. The trees, which grow to a maximum height of 25 feet in the wild, will only grow to 10 feet if kept in pots. For that reason, and because they are not generally frost hardy, kaffir lime trees are often grown in containers.
Kaffir lime trees thrive in warm, humid climates. In the America, they can only be grown outdoors year-round in United States Department of Agriculture (USDA) plant hardiness zones 9 to 11, according to the University of Oklahoma. In cooler climates, they can be grown in a pot and brought indoors when cold weather arrives.
Like most citrus trees, kaffir limes need full sunlight to bloom and fruit successfully. They will grow in locations with dappled afternoon shade in the hottest USDA hardiness zones.
Soil and Water
Citrus hystrix trees thrive in rich, loamy soils. The soil should be well-draining. Container trees grow best in soil that is composed of two parts peat moss, one part sand and two parts loam. Kaffir limes do best when the soil is allowed to dry down to 1 inch below the surface before watering, according to the website Thai Food and Travel. Simply insert your finger into the soil to test for moisture. Water slowly and deeply when watering, and continue until the water drains freely from the bottom of the pot, or collects on the surface of the soil.
Kaffir trees will bloom year-round, so fertilize once per month with a water-soluble, balanced (10-10-10) fertilizer formulated for citrus trees. Apply the fertilizer according to the directions on the label as indicated for the size of your tree.
Prune after new growth starts in the spring. While outdoor trees will not require pruning other than to remove crossed, damaged or broken branches, indoor or container trees can be shaped according to the home gardener's style and to contain the size of the tree.