Kaffir Lime Trees : How to Plant, Grow & Care

The kaffir lime tree, also known as makrut, yields strongly flavored leaves and distinctive bumpy fruit. Our guide explains how you can Plant, grow and care for them at home!

Are you a fan of Thai cuisine? If so, you’re likely familiar with the key ingredients that make a great Thai curry. One of those essential ingredients can be grown right in your own garden. If you enjoy stir-fries and the bright flavor of lime zest, consider growing a kaffir lime tree!

While these trees originate from tropical Southeast Asia, they are surprisingly easy to grow outside that region. With a bit of care during the colder months, you can enjoy kaffir lime year-round. Alternatively, you can opt to grow kaffir lime indoors and skip outdoor cultivation entirely.

Citrus plants can grow quite large in their natural environments, but with the right care, they can easily stay compact. Your trees can thrive in a greenhouse, on a patio, or even indoors. Just be mindful of the thorns!

Let’s talk about what might become your new favorite potted plant, or perhaps your top choice for growing a tropical plant in the southern United States.

Concise Care Guide

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Kaffir Limes: Key Information

Kaffir lime, also known as makrut lime (Citrus hystrix), originated in Southeast Asia. The term “kaffir” has historically been used as a racial slur against non-Muslim Swahilian Africans who were taken during the Indian Ocean slave trade. Additionally, the Kaffirs were an ethnic group in Sri Lanka with Bantu ancestry.

Due to evolving perspectives on the use of certain names, many restaurants and grocery stores now refer to the lime as makrut lime. The term micrantha, which also denotes a lime with a long history, actually refers to the same species as C. hystrix. To promote sensitivity and respect, many prefer to use the term makrut when talking about this citrus plant.

This citrus tree is an evergreen shrub that can grow between 6 and 35 feet tall. It features double hourglass-shaped leaves, with the leaf blade being twice the size of the petiole, growing on thorny branches from a central trunk. In spring, the tree produces white flowers with four to five petals, each up to 2 inches wide, which are capable of self-pollination. After flowering, green citrus fruits with a bumpy texture develop where the flowers were. As they ripen, the fruit turns yellow. When grown indoors, home gardeners may need to hand-pollinate the kaffir lime tree.

Crushed kaffir lime leaves release a strong citrus aroma and add a unique flavor to various dishes. The fruit rinds have a tangy taste and are commonly used in curry pastes. They are also zested into spiced rum. Beyond culinary uses, the rind is believed to repel mosquitoes, fleas, and lice. Fresh juice from the fruit is diluted with water and used as a cleaner. Additionally, makrut lime essential oil finds applications in several industries, including aromatherapy.

Since this plant takes several years to bear fruit (at least three years from the sapling stage), many gardeners prune it to maintain a manageable size for large containers. This can be challenging due to the thorns, which can grow up to 1.5 inches long. Some gardeners graft less thorny citrus varieties onto the makrut lime to reduce thorniness in future growth, though this results in a tree that produces mixed fruit. Additionally, grafting makrut branches onto different citrus rootstocks is a common practice.

How to Plant Kaffir Lime Tree?

In the Western Hemisphere, most people grow their kaffir lime tree in a large planter, ideally at least three feet deep. The kaffir lime tree thrives in tropical climates. If you live in a tropical area and are already growing other tropical plants, plant the kaffir lime tree outdoors in late fall, allowing it time to establish its roots before the summer heat arrives. Avoid transplanting in the middle of winter or in cold weather, as this could jeopardize the plant. Position the tree away from other fruit trees, as well as from your house and other structures. Under optimal conditions, kaffir lime trees can grow up to 35 feet tall.

Dig a hole that is at least 3 feet wide and twice the width of the root ball. Enhance the soil in the hole by mixing in sand for improved drainage and well-rotted compost. Place the kaffir lime tree in the hole, then fill it with regular garden soil. Ensure that the tree’s root mound remains above the soil level and that any graft joints are exposed.

If you live outside tropical regions, transplant the kaffir lime tree from its nursery pot into a large container filled with a similar soil mix to what an outdoor tree would use. Air Pots available in our store are a great option for this. When colder weather arrives, you can bring your kaffir lime tree indoors to protect it.

Caring Kaffir Lime Tree

Let’s discuss the essential requirements and growing conditions for your kaffir lime trees. With the right care, you’ll enjoy a plentiful harvest of kaffir lime leaves throughout the year.

Sunlight and Temperature Needs

Makrut trees thrive in tropical climates and require full sun, meaning they need at least 6 to 8 hours of sunlight each day. They are suited to USDA hardiness zones 10 to 12. These trees handle high temperatures well, including triple-digit heat. However, when temperatures drop below 50 degrees Fahrenheit, you should protect your tree. Bring it indoors or cover the leaves with a commercial frost cloth to shield it from the cold. Exposure to hard freezes can be fatal, and temperatures below 50 degrees can also inhibit flowering and fruit production.

Watering and Humidity

These plants thrive in high heat and humidity. If you live in a dry climate and your tree is outside, water it a couple of times a week at the base of the trunk, preferably in the morning, and avoid wetting the leaves. Providing about an inch of water per week is generally sufficient if the humidity is adequate. Ensure the soil dries out between waterings to prevent waterlogging.

Drip irrigation or soaker hoses are ideal for this purpose, but other gentle irrigation methods can also be used. Avoid watering if there has been significant rainfall. During the growing season, particularly when the tree is fruiting, increase watering to a few times per week to support fruit development and growth.

Soil Requirements

The soil around your tree should be of average to fertile quality and sandy to ensure proper drainage. When preparing a pot or planting hole, use a blend of average garden soil mixed with sand and well-rotted compost. While makrut trees can tolerate less ideal soil conditions, they require excellent drainage in their container or planting area. Ideally, the soil pH should be between 6 and 6.5.

Fertilizer Guidelines

Once the tree has completed its first year of growth, apply a slow-release citrus fertilizer 2 to 3 times annually. Even for mature trees, a few tablespoons of fertilizer are sufficient. Apply it at the start of spring, early summer, and late summer. Avoid fertilizing during winter, as this can stress the tree. The fertilizer should have an NPK ratio of 2-1-1. Be sure to water the area thoroughly after application.

Pruning Tips

When pruning a kaffir lime tree, wear durable, thick gloves to protect yourself from its thorns. Use loppers for the task. Always cut at the node of each branch unless removing a section due to disease. Trim branches back by a few inches if they appear to be weeping. Regular pruning is crucial if you wish to maintain a smaller size for the tree.

Start by removing any branches affected by disease. Then, cut away any dead branches that are dark brown and dry beneath the bark. To check if a branch is dead, scratch its surface. Next, remove small sprouts from the lower 10 to 12 inches of the tree, which can be saved for propagation into new trees. Also, remove any branches growing towards the trunk’s base. Remember, kaffir lime trees are evergreen, so they won’t shed their leaves in winter.

How to Propagate Kaffir Lime Trees?

Small buds and suckers you’ve pruned from the tree can be used to grow new plants in a starter pot. To encourage rooting, use a propagation dome along with rooting powder or gel. Cleanly cut the ends of the cuttings and remove the lower leaves. Dip the tips of the cuttings into rooting media and place them in rapid rooters. Arrange the cuttings in the tray with enough space to avoid contact. Lightly mist them with water and cover the tray with the dome. Keep the tray in a low-light area at room temperature. Rooting can take anywhere from 6 days to 6 weeks.

To graft your lime onto a different rootstock (which could be another makrut or a different lime species), start by taking a healthy branch cutting and making a 45-degree angle cut at the base of the stem. Then, prepare the rootstock branch by cutting it to expose the healthy tissue. Make a small cut into the bark just enough to separate it from the flesh, and insert the makrut cutting underneath the bark. Secure the graft with plastic wrap and cover the grafted area with a plastic bag, sealing the edge to the rootstock. After a few weeks, remove the plastic bag and wrap. Success is indicated if the branches have fused together and show new growth.

How to Harvest and Store?

Despite the thorns and the potential for pain, harvesting from this tree in your garden is truly satisfying! Whether you’re collecting fragrant leaves, fruit, or juice, you’ll have astringent flavors to enhance your dishes throughout the year.

Harvesting

Harvest green kaffir lime leaves from the tree once it’s mature, typically in spring when the leaves are fresh. Use them in dishes like fish, chicken, or spicy foods as desired. For small amounts, plucking the leaves by hand is sufficient. For larger quantities, it’s better to cut an entire branch and remove the leaves carefully. Wearing gloves is recommended for this task.

The fruit usually starts to form about 6 to 9 months after the flowers have faded. To determine if the limes are ready for harvest, pick one and cut it open. If it has sufficient juice, the remaining limes are likely ready as well. Always harvest the fruit while it’s still green, as yellow limes can be too bitter, though their zest can still be used in cooking. In tropical regions, you can collect the fruits year-round, while in colder zones, the harvest typically occurs in late summer.

Storing

Here’s how to properly store your kaffir lime leaves and fruit:

Fresh kaffir lime leaves should be washed and kept in a plastic bag with paper towels in the refrigerator’s crisper drawer, where they’ll stay fresh for about a week. If you want to store them longer, you can freeze them in this way for up to a year. To dry the leaves, hang an entire branch upside down in a warm, dark, and dry location until they become brittle. Once dried, place them in an airtight container, where they will remain good for up to two years.

For fresh kaffir limes, store them on the countertop with good air circulation for 2 to 4 weeks. In the refrigerator, they can last 1 to 2 months. Cut limes should be used immediately or within a day. Lime juice can be kept airtight in the refrigerator for up to 6 months. While freezing whole limes is not recommended due to texture changes, you can freeze lime juice without issue.

Dehydrated limes can be stored in a plastic container or glass jar for up to 5 years. Properly canned and sealed lime jars can last 9 months. You can also freeze lime zest, either whole or in sections, for up to a year, and use it to add a fresh fragrance to your dishes.

Common Issues and Solutions

We’ve discussed the care aspects, so now let’s focus on the issues to watch for when inspecting your tree.

Growth Issues

If this tree is exposed to temperatures below 50 degrees for extended periods, it may suffer from cold damage or even die. If you anticipate cold weather, move the tree indoors to protect it.

Planting the tree in soil with poor drainage can cause stress and make it susceptible to diseases. Conversely, overly dry conditions can lead to leaf drop and reduced flowering, which impacts your harvest. Nutrient deficiencies, indicated by changes in leaf color, can also slow growth and yield. To prevent this, fertilize the tree 2 to 3 times during the growing season.

Pests

Ants often indicate the presence of other pests, as they feed on the honeydew excreted by insects like aphids. By attracting these pests, ants create a food source for themselves and the aphids. To address this issue, mix equal parts borax, peanut butter, and honey into a paste and place it in old bottle caps around the base of the tree. The ants will transport the paste back to their colony, where the borax will eliminate them. Additionally, applying a sticky substance like Tanglefoot Trap to the tree trunk can help keep ants away from the fruit.

Cottony cushion scale is a frequent issue with citrus trees, appearing as white, fluffy bumps on branches and trunks. This problem is caused by the Icerya purchasi insect, not a disease or fungus. These pests feed on the sap of the tree and can excrete honeydew, which attracts ants. To manage a small infestation, use a cotton swab dipped in rubbing alcohol to dislodge the scales. For more extensive infestations, neem oil or horticultural oil can effectively eliminate these scale insects and other mealybugs.

Mealybugs, spider mites, leaf miners, and whiteflies are common pests that feed on the sap of the makrut tree’s leaves and branches. Mealybugs appear as small, cotton-like clusters residing in colonies on the tree. Spider mites are very tiny and may not be noticeable until they begin to spin webs around parts of the tree. Leaf miners burrow inside the leaves, consuming the tissue between the cell walls, leaving behind winding trails. Whiteflies are tiny, moth-like insects that feed on sap from various parts of the tree.

To address these pests, start by thoroughly inspecting the tree and using a strong stream of water to dislodge the insects. This method often resolves the problem. Neem oil is useful for treating eggs of many pests, as it suffocates the unhatched larvae, and it also works against adult spider mites. Treating citrus leaf miners is more challenging; remove and dispose of leaves with visible mining trails, then regularly spray the tree with neem oil. The azadirachtin in neem oil will gradually penetrate the leaves to eliminate any remaining larvae. For adult mealybugs and whiteflies, insecticidal soap is an effective solution.

Diseases

Citrus canker is caused by the bacterium Xanthomonas axonopodis pv. citri. This disease results in yellow-ringed lesions appearing on the leaves, branches, and fruit of the tree. As the disease progresses, these lesions develop a gray, fuzzy center, leading to defoliation. To manage citrus canker, promptly remove any affected parts of the tree. Apply a copper fungicide spray according to the manufacturer’s instructions, ensuring thorough coverage of all tree parts.

It’s crucial to notify your local agricultural extension office about the citrus canker outbreak, as some areas have regulations that may require the tree to be removed to prevent the spread of the disease. Copper fungicide may not completely eradicate the disease, and there is a possibility of losing the tree despite treatment efforts.

Greasy spot is caused by the fungus Mycosphaerella citri. It begins as a spot on the underside of leaves, which may eventually develop into a yellow, greasy, and shiny spot on the upper side. The fungus can also affect the fruit, resulting in dark patches known as greasy spot rind blotch, posing a major issue for fruit producers. Copper fungicides are effective in treating this fungus, but they are often combined with horticultural oils before application.

Phytophthora gummosis, caused by two soil-borne pathogens, leads to foot rot in kaffir lime trees, resulting in the decay of the roots. Symptoms include cracked bark with a gummy substance oozing from the cracks and discoloration of the bark above the roots, turning brown to black. Treating root rot from Phytophthora is challenging. You may consider grafting resistant rootstock onto your tree or applying treatments similar to those used for greasy spot to address the issue.

Huanglongbing (HLB), commonly known as citrus greening, is a bacterial disease that impacts nearly all citrus plants. It causes new leaves to develop a mottled appearance and can lead to fruit with undeveloped seeds. Additionally, fruit on trees affected by HLB may fail to ripen properly. If you observe these symptoms, isolate the affected tree and reach out to your local agricultural extension office for guidance on the appropriate actions to take.

FAQs

How tall can a kaffir lime tree grow?

A kaffir lime tree can reach heights ranging from 6 to 35 feet, depending on its growing conditions.

How does kaffir lime differ from regular lime?

Kaffir limes are characterized by their bumpy texture, thorny branches, and a more pungent, astringent aroma and flavor. The leaves of the kaffir lime tree are especially prized for their culinary uses.

Why are kaffir lime leaves so pricey?

The high cost is often due to the thorns on the tree, which make harvesting challenging and require careful handling to avoid injury.