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Figure 1. Greasy spot on undersides of leaves. |
R.L. Phillips, S. Goldweber, and C.W. Campbell2
Hot semitropical, subtropical, and tropical regions of the world. Major producing countries are India, Mexico, Egypt, and the West Indies. Naturalized in hammocks, coastal areas, Florida Keys, southern Florida, tropical America.
Key lime originated in southern Asia and was carried by the Arabs across North Africa into Spain and Portugal. It was brought to the Americas by Spanish and Portuguese explorers in the early part of the sixteenth century where it escaped cultivation and became naturalized in parts of the West Indies, some Caribbean countries, and southern Florida. See Table 1 for summary information on Key lime.
Table 1. Key lime origin.
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Common Name |
Scientific Name |
Origin |
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West Indian' lime |
Citrus aurantifolia Swingle |
Southern Asia |
The commercial lime industry is based on the `Key' lime in areas other than the United States. Most of the crop is used fresh in limeade, mixed drinks, pies, and iced tea, and is squeezed onto seafood or other foods to bring out the flavor. It is also used in bottled lime juice and carbonated beverages. The principle by-product is lime oil, used in cosmetics and flavoring.
Tree. Small, bushy tree, rarely taller than 12 feet with slender branches armed with short spines. Its dense foliage consists of small, pale green, blunt-pointed leaves with narrowly winged petioles (leaf stalks). Spineless selections are more compact and upright in growth, have darker green foliage, and are characterized by low yields.
Flowers. Small and white, in axillary clusters (around the stalk). Flowering occurs throughout the year but mainly in the spring.
Fruit. Very small (1 1/2 to 2 in.), round to oval. Very thin, smooth and leathery rind, greenish yellow at maturity. Flesh greenish yellow, juicy, highly acid with distinctive aroma. Moderate number of seeds, which are highly polyembryonic (two or more plants from one seed).
Season. Some fruit mature on the tree year round. Principal season is summer in south Florida and later further north.
Key lime is precocious (develops exceptionally early) when grown from cuttings or air layers and may produce some fruit within a year of planting. Budded trees should produce fruit within 3 years, while seedling trees require another year or two before fruiting.
Key lime is frequently propagated from seed since it is true-to-type due to its high degree of polyembryony. Key lime may also be propagated with hard wood cuttings, with air layers, or as budded trees with rootstocks resistant to foot rot and suitable to local soil conditions.
The Key lime is very sensitive to cold temperatures, which limits it to warm areas of southern Florida. Locally cold locations within a given area may be hazardous whereas some locally warm locations outside an area may be suitable. Trees should be planted in locations sheltered from cold north winds. Key lime has a high total heat requirement for the production of good sized fruit.
The Key lime is well adapted to a variety of soils. It was formerly grown commercially and is naturalized in the Florida Keys where it is well suited to the rocky alkaline soils. However, salt damage is a frequent problem there. The tree grows more vigorously in deep sandy soils but tends to have fewer fruit that are larger and less juicy and have a thicker peel. Key lime requires good drainage and does not tolerate flooded conditions.
The preferred time to plant is late winter or early spring, although potted trees may be planted any time in warm locations. At least 12 feet of growing room in all directions should be allowed for each tree. The best planting sites have good drainage and air circulation, are sunny, and are protected from cold north winds.
Remove weeds from the planting area. In most soils, dig a hole slightly wider than the container but, in Rockland soils, dig the hole at least twice the width and depth of the container. Set the tree in the ground slightly higher than it was growing in the container. Refill the hole around the plant, applying water and tamping as you do so to eliminate air pockets. Form a basin around the tree and water 3 times a week for 3 weeks, tapering of to once a week during dry periods. Keep the area around the tree weed-free to reduce competition. Do not allow the tree to wilt, but do not overwater. Too much water can damage roots, especially in poorly-drained soils. Prune only to shape the tree and to remove sprouts on the trunk. Fertilize after the first growth appears with 1/2 pound of mixed fertilizer and every 6 weeks for the first 3 years. Apply nutritional sprays 3 times per year or as needed.
Fertilize sparingly (less than other citrus) to avoid disease problems associated with luxuriant growth. Apply to the entire root area 3 times a year in winter, late spring, and fall. Apply nutritional sprays as needed to prevent or correct deficiencies. Prune only to shape or remove dead wood since dieback (dying of peripheral parts) and poor wound healing may result.
Key lime can be successfully grown in most areas without insect or disease control sprays, although the fruit may be less attractive. Natural biological control assists in keeping most pests at a low level. Make periodic inspections, however, to determine outbreaks that require treatment. Planning a spray program is complex because of the variety of pests, chemicals, and changing government regulations. Consult your county Extension agent before beginning treatment.
Key lime is highly susceptible to lime anthracnose (withertip, blossom blight). This disease results in lower fruit production due to blasting or withering of buds and blossoms. Young shoots may be killed and young fruits shed prematurely or develop small, round areas of dead tissue (necrotic lesions). Avoid wetting the trees with sprinklers, especially in the evening and during blooming. Avoid overfertilization since lime anthracnose thrives on luxuriant growth. Copper sprays have been used for control but are often not satisfactory because Key lime usually has new growth.
Diplodia dieback can be a serious fungus problem. There may be drooping, wilting, and dieback of twigs on scattered branches, with whole branches affected eventually. For more information and control measures, consult your county agricultural extension agent. Greasy spot can cause serious leaf loss. Look for slight blisters like irregular flecks of grease on the undersides of leaves ( Figure 1 ), with corresponding yellowed or light spots on the upper side. Future outbreaks can be prevented by timely sprays of benomyl or copper. Foot rot can attack the trunk and crown roots and seriously damage the tree. Fungus-caused lesions usually appear near the bud union ( Figure 2 , Figure 3 ). There may be some gum oozing. Affected bark eventually dries, cracks, and drops off. This disease is easier to prevent than treat. Preventive measures include maintaining a weed-free area around the trunk, planting high in well-drained soils, using resistant rootstock, and pruning to keep lower limbs off the ground.
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Figure 1. Greasy spot on undersides of leaves. |
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Figure 2. Fungus-caused lesions near the bud union. |
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Figure 3. Another example of fungus-caused lesions near the bud union. |
1. This document is Fact Sheet FC-47, a series of the Fruit Crops Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: February 1991. Revised: April 1994.
2. R. L. Phillips, former Extension Horticulturist, Fruit Crops Department; S. Goldweber, Extension Agent III, retired; C. W. Campbell, Emeritus Extension Horticulturist, Tropical Research and Education Center, Homestead, FL, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
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Boards of County Commissioners Cooperating. Larry Arrington, Dean.
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