Scientific Name: Citrus aurantiifolia

Aliases: key lime, mexican lime, west indian lime, bartender's lime, florida lime, florida keys lime

Family: Rutaceae (citrus or rue family)

Mature Plant Size: Up to 10-16' tall by 4-8' wide; generally up to 5-7' tall by 2-4' wide when grown indoors in containers

Type: Tree, Woody Shrub

Growth Rate: Medium in warmer climates, slow to medium in more temperate climates

Light Requirements: Bright, full sun; at least 8 hours sunlight per day; will tolerate partial sunlight in warmer climates; environment changes must be gradual to prevent leaf drop

Moisture Requirements: Water thoroughly and infrequently during active growth to maintain moist to semi-moist soil; will not tolerate soggy soil; requires excellent drainage; do not overwater or let container sit in water; reduce watering during dormant periods/winter

Soil Requirements: Prefers sandy, well-draining soil with a pH between 6.8-7.8 or a commercially available citrus soil mix; tolerates acidic soil with a pH as low as 6.0; will not tolerate salty soil

Natural Habitat: Originally native to Southeast Asia, most likely China; then gradually introduced to the Middle East, North Africa, Europe, and finally the West Indies and Mexico, including the Florida Keys; derives its name from the Florida Keys after a hurricane destroyed large crops in other areas of the US

Care Recommendations: Key lime trees prefer temperatures between 58-75 degrees F and humidity levels between 30 and 65 percent. Outdoors, the Key lime tree is considered hardy to approximately 30 degrees F, or in USDA zones 9, 10, and 11. Key lime trees require at least 8 hours of direct sunlight per day for proper growth as the plant's food supply is stored within its leaves. The soil for the Key lime tree should be kept semi-moist to moist during active growth, and watering should be reduced slightly in winter months. Soil should never remain soggy and the container must never be allowed to sit in standing water. This plant may be fed accordingly up to every two months during active growth with a citrus or acid plant food. During bloom, flowers may require manual pollination if the tree is kept indoors, which may be performed lightly with a cotton swab. Although Key lime tolerates being pot-bound well, it should be repotted every 3 years or so into a container 1-2 inches larger in diameter, or roots may be trimmed back up to 10 percent and it may be repotted into the same container with new soil to provide fresh nutrients. The Key lime tree may also be lightly pruned back in the spring to produce a bushier looking tree.

Propagation: Key limes trees are best propagated by sowing seed or by stem cuttings. Stem cuttings may be taken in late spring or early summer, dipped in rooting hormone powder, and planted in an appropriate sterile soil with temperatures of at least 70-80 degrees F to accelerate rooting. In commercial environments, Key lime is commonly propagated by grafting to rootstock of other citrus or dwarf trees. Propagation by seed requires sterile potting mix, temperatures of at least 70-80 degrees F, and may take up to 3-6 weeks for seeds to germinate. Note that seed propagation may yield up to two plants, as Key lime seeds are polyembryonic. However, the homozygous plant usually survives, allowing the majority of Key lime trees grown from seed to be true-to-type. Note that stem cuttings generally produce blooms within 1-3 years and that propagation by seed may take up to 3-5 years for plants to begin flowering.

Pests and Diseases: Key lime trees are susceptible to aphids, mealybugs, scale, and spider mites. Spider mites may be controlled by raising humidity levels, and other insect pests may be controlled by showering the tree or by using horticultural oil for more severe infestations.

If humidity levels are too low, the tree may begin to drop leaves. To raise humidity, a humidifier may be used or the container may be placed on a pebble tray, but the plant should never be allowed to sit in standing water. Overwatering frequently leads to root rot. Key lime and most other citrus should be gradually acclimated to new lighting conditions by incremental exposure to differing sunlight over the course of several days. Drastic change in lighting conditions, such as moving outdoors in full sun from protected/filtered sun may lead to leaf and bloom drop by shocking the plant. Another cause of yellow leaves is sometimes improper or insufficient fertilizer.

Additional Information:

Key lime should not be confused with the Persian lime, which is your typical supermarket variety green lime. Note that Key limes have round fruit that is generally 1-2 inches in diameter, and that their fruit is yellow when ripe but is usually green (unripe) when sold commercially. The Key lime is smaller, has higher acidity, and a thinner rind than that of the Persian lime (Citrus latifolia).

The Key lime tree is commonly grown as dwarf citrus and is suitable for containers both indoors and outdoors. Note that Key lime trees have several thorns.

The Key lime tree (Citrus aurantiifolia) may bloom twice per year when at least 3 years old and often blooms and produces fruit continuously when mature.