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Finger Lime Tree: The Caviar Of Citrus

Finger limes are slowly being introduced into the culinary world, but quickly becoming chefs’ favorites. Finger limes are described as citrus caviar because the texture of the pulp resembles caviar. The pulp contains small round vesicles filled with juice that provide a burst of refreshing acidity and flavor with every bite. Growing a finger lime tree is incredibly easy and the fruit can be stored in the freezer to be enjoyed any time of the year. 

The juicy pearls of finger lime fruit can be used as a garnish on an endless amount of dishes and desserts. They pair particularly well with seafood but can be added to cocktails and desserts. It is an excellent substitute for lime juice and in some cases a better option. Using finger limes in tacos and fruit salad adds the delicious lime flavor without making your tortilla soggy or the fruit salad watery. If you are a fan of tangy flavor, you can even eat these on their own. 

Finger lime trees can be incorporated into almost any space. They are low maintenance and thrive in the heat, but will need protection from frost. Luckily, they grow well in containers so bringing them indoors during the winter is a great option for cooler climates. Finding a finger lime tree may be your biggest challenge. They are seldom found in stores, but there are a handful of online retailers that can ship directly to your home.

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Quick Care Guide

Finger lime tree
The finger lime tree produces small fruit packed with juice-filled vesicles. Source: mmmavocado
Common Name(s)Australian Finger Lime, Finger Lime, Caviar Lime
Scientific NameMicrocitrus australasica or Citrus australasica
Days to HarvestHarvest annually March-May
LightPartial to full sun
WaterModerate
SoilWell-draining
FertilizerEvery 6 weeks from spring-summer
PestsMites, scales, lepidopterans, aphids, ACP
DiseasesPhytophthora, twig dieback, HLB
Finger lime
Most finger limes are not very large, but they’re packed with flavor. Source: RBerteig

Microcitrus australasica is commonly referred to as finger lime, Australian finger lime, and caviar lime. Despite looking quite different, Australian finger limes are related to common citrus types such as lemons, navel oranges, and mandarins. Microcitrus australasica is one of six native citrus species to Australia where it grows in the rainforest as an understory shrub or small tree. Shrub and tree size varies between 6-25 feet. The Australian finger lime tree has small, opposite, evergreen leaves with a thorn at each leaf axil. The flowers are bright pink fading to pale pink or white. Fruit is long, cylindrical, and often curved; some say resembling fingers. Fruit is typically seedless or contains very few small seeds.

Depending on the variety, fruit size ranges from 1.5-5.5 inches and colors include red, yellow, green, purple, and brown. In Australia there are several established varieties available however there may be fewer options available in other countries. Some examples of popular varieties include ‘Red Champagne’, ‘Chartreuse’, ‘Crystal’, and ‘Pink Ice’. Each variety has a different sugar-acid ratio giving them each a unique flavor. They also have different colored pearls or vesicles. 

Australian finger lime trees are typically planted as grafted trees and will start producing 1-2 years after planting. It takes 4-5 years for the tree to produce an abundance of fruit. Trees flower in the fall and are ready for harvest between March and May. Some varieties may produce a month earlier or later. Finger lime trees are self-fertile but will yield a heavier crop when pollinated.

Microcitrus australasica is not only special for its unique fruit. It may be the key to finding a cure or solution to Huanglongbing (HLB) or citrus greening. HLB is a disease that causes small and deformed fruit and the eventual death of citrus trees. It has been devastating to citrus producers around the world, especially in the United States, China, and Brazil. Australian finger lime has shown both tolerance and resistance to HLB. Tolerance means that the trees become infected, but the symptoms are mild and the tree can grow and continue producing marketable fruit. Resistance is when the tree is not susceptible to the HLB and does not become infected after exposure. Understanding and utilizing these traits are crucial to protecting citrus production around the world. 

Planting

The best time to plant a young tree is in the spring after the last frost. It can also be planted through the summer, but avoid temperatures that exceed 90°F for a couple of weeks while the tree acclimates. Choose a sunny, warm location with good soil drainage. Keep in mind, this tree has a lot of thorns, so avoid planting in high traffic areas where people or pets may accidentally come in contact. Shelter from wind is also important. Excessive wind can cause the thorns to damage or puncture the fruit. 

This tree can be planted in a large container or in the ground. If planting in a pot, use at least a 10-gallon pot and a potting mix specifically formulated for citrus. Water in the newly planted tree until the entire pot is saturated. When planting in the ground, dig a hole twice as wide and just as deep as the root ball. Fill in the hole, cover with mulch, and water in. Whether planting in a container or the ground, do not bury the graft union. The rootstock should be at least a few inches above the soil level.

Care

Finger lime flower
Citrus australasia flowers are small but pretty. Source: Rod Waddington

Caviar limes require very little effort to grow. Providing the best care for your tree will keep it looking beautiful and productive. 

Sun and Temperature

Australian finger lime requires partial to full sun meaning at least 6 hours of direct light per day. They are hardy to zones 8-11 but can be grown in colder regions if brought inside during frost.

Finger limes thrive in temperatures above 90°F during the summer and mild winters above 40°F. Trees require protection during the winter if temperatures drop below freezing.

Water and Humidity

Water in the morning once or twice a week. Soil should be kept moist, but not soggy or saturated. Soaker hoses or drip irrigation should be used for irrigating to avoid water runoff.

Finger limes planted in containers may need to be watered more often. They should be fully saturated and allowed to dry down until slightly moist before the next watering. Potted trees can be watered using drip irrigation or manually with a hose.

Do not allow the soil to dry and keep plants well-watered during flowering and fruit development. Underwatering during the warmer months can lead to leaf drop. Trees do not need extra water during rainy seasons. 

Soil

Australian finger lime can grow in a wide range of soil types as long as it is well-draining. They prefer loamy soils with high organic matter. For optimal growth, the soil pH should be slightly acidic to neutral.

Fertilizing

There are a lot of different fertilizers available specifically formulated for citrus. The rates and application frequency depend on the fertilizer blend and whether or not it is a slow-release blend. Slow-release blends typically need to be applied once or twice a year.

Fertilize finger limes in the spring and summer. Keep in mind, Australian finger lime does not require as much fertilizer as other citrus types such as a lemon or mandarin tree. Do not over-fertilize during bloom and fruit development because it may cause the flowers and fruit to drop. If a citrus fertilizer mix is not available, 12-6-6 can be used. Look for fertilizer blends that also incorporate micronutrients such as magnesium, zinc, iron, and copper.

Pruning

Finger lime thorns
Be careful and use protective gear as finger lime trees have very sharp thorns. Source: Starr

Pruning can be done at any time during the year, but it’s best done after harvesting to avoid removing flowers and fruit. Typically fruit is ready to harvest March-May and flowering begins in the fall. Australian finger lime is difficult to prune because it is full of thorns. Use hand and eye protection when pruning. Heavy-duty, puncture-resistant work gloves are highly recommended.

Pruning should be done to maintain size, remove troublesome branches, and remove dead shoots. Finger limes do not require old growth to produce fruits. Most fruit will naturally fall off the tree. Manually remove any old fruits that do not fall off naturally. Australian finger trees are not deciduous, so leaves will remain on the tree the entire year.

Propagation

Grafting and rooted cuttings are the best methods for propagating Australian finger lime. Seeds can be difficult to find and successful germination is rare.

Chip budding is the most commonly used technique for grafting Australian finger lime and is typically grafted onto a rootstock seedling. If planting in the ground, grafted trees are the best option. Seedlings typically have better root structure than rooted cuttings making the tree more stable. Depending on the type of rootstock, they can provide disease resistance, greater cold tolerance, and height control.

Rooted cuttings are a very simple way to propagate Australian finger lime. Cuttings should be between 2-4 inches and a rooting hormone should be used to speed up root formation. Keep the cuttings in a humid environment away from direct light until roots have been established. Cuttings will take around two weeks to start developing roots. Slowly acclimate over 1-2 weeks before exposing to direct sunlight. Trees propagated by cuttings are most suitable for containers and should not be planted in the ground.

Harvesting and Storing

Caviar limes
The “caviar lime” can grow in shades of red, brown, pink, green, or purple. Source: Tatters

Harvesting finger lime fruit is not a fun task without proper protection. These thorny plants can make harvesting a nightmare if you aren’t careful. Once the fruit is picked, there are a few options for storing to make sure your hard work doesn’t go to waste!

Harvesting

Color is the first indicator for determining if finger limes are ready to harvest. Depending on the variety, finger lime fruit can be red, yellow, green, purple, or brown.  Once they are showing full color, gently pull the fruits. Ripe fruit will easily come off the tree. If the fruits need to be forced, then it’s not fully ripe and ready to harvest. When harvesting fruits, it is wise to wear thick, impenetrable gloves to avoid being pricked by thorns.

Storing

Fruits can be stored at room temperature for about a week and in the fridge for about 3 weeks. Keep refrigerated fruits in a breathable bag or container.

Surprisingly, caviar limes store well in the freezer. To freeze, place whole fruits in a sealed freezer-safe container. The pulp maintains its “caviar” texture and can be stored for 6 months.

Troubleshooting

Australian finger lime foliage
Finger lime leaves are pretty and have a rounded to slightly pointed shape. Source: Starr

Australian finger limes occasionally have minor growing issues. Most issues can be prevented or easily resolved. Below are some tips for having a problem-free growing experience. 

Growing Problems

Despite being shade tolerant, finger lime trees may produce little or no fruits if given too much shade. The plant will continue to survive and grow, but fruit production will be compromised.

Flower abortion and premature fruit drop are commonly caused by extreme weather and over-fertilizing during flowering or when the fruit is first starting to develop. Do not fertilize during flowering or the primary stages of fruit development to prevent unwanted fruit loss. Some flower and fruit drop is normal and to be expected.

Damaged fruit is a common issue, especially in windy areas. The thorns create open wounds in the fruit leading to mold and rotten fruit. Avoid planting in windy areas or provide a wind barrier when the fruit is developing. 

Pests

There are a few species of mites that are problematic to caviar limes. Mites are extremely small arachnids that are difficult to notice with the naked eye. They cause stippling damage to the leaves and heavy infestations will cause leaf drop. Usually, the damage is noticed before the pest. All adult mites are small, eight-legged, and tend to stay in clusters on the undersides of leaves. Some mites produce webbing while others don’t. Colors range from creamy yellow to dark red. Mites tend to attack weak or stressed trees. Maintaining a healthy tree is the most important defense against mites because they tend to have a good balance between pest mites and predatory insects to keep the populations under control. If mite populations get out of control horticultural oils and insecticidal soaps can be used to knock down heavy infestations.

Soft and armored scales can be found on the twigs and branches of trees. There are several species of scale in a variety of colors ranging from yellow to brown to black. Damage does not come directly from the scale. Scales produce excessive amounts of honeydew which leads to sooty mold. Sooty mold covers the leaves which inhibits photosynthesis and leads to leaf drop. Scales are usually controlled by natural predators and parasites. If treatment is necessary, oil sprays are effective.

Aphids are a small soft-bodied insect that feeds on the sap of tender plant tissue. They come in a variety of colors such as yellow, orange, green, and black. Similar to scale insects, they produce honeydew which can lead to other problems like sooty mold. Aphids are usually controlled by natural predators; however, populations can still become off-balanced and damaging. Aphids can be controlled by manually removing leaves with heavy infestations and by hosing them off with water. Horticultural oils and insecticidal soaps are also effective in controlling aphids.

Lepidopteran pests include several types of moth larvae that cause damage to the leaves. There are a few leaf roller species that cause damage to the tender new growth. Citrus leaf miner is also a lepidopteran pest that causes mining damage typically on the undersides of leaves. Mining damage looks like tunnels underneath a shallow layer of the leaves. Lepidopteran pest damage is mostly cosmetic but can stunt growth in young trees. Larvae can be manually removed on young trees. Treatment should not be necessary on mature trees. If citrus leaf miner damage is bothersome, pheromone traps can be placed on trees to disrupt mating.

Asian citrus psyllid (ACP) is a small mottled brown insect about the same size as an aphid. Nymphs are yellow to green and lay flat on leaves and twigs. These psyllids produce white spindly excrement, which makes identification easier. Psyllids inject a toxin during feeding which may cause burn back on tender growing tips. However, feeding damage is not the main concern. They are considered a major pest because it vectors HLB. Research has shown that ACP is not nearly as attracted to Australian finger lime as other types of citrus. However, it’s important to monitor your tree and be aware of the pest to help prevent the spread of HLB. Depending on your area, the presence of ACP will warrant different responses. It’s best to research the local regulations and reach out to your county office if there are any questions.

Diseases

Phytophthora is one of the most common root diseases in citrus. It causes a general decline in trees. The leaves will look yellow or a light green color. Advanced stages will present “gumming” or sap oozing from the trunk of the tree. Trunks may also exhibit a water-soaked appearance.  Phytophthora is prevented by using best irrigation practices and planting in well-draining soil. Some rootstocks are resistant or more tolerant of phytophthora. It is extremely important to leave at least a few inches of the rootstock above the soil line. There are beneficial microbes and mycorrhizae products that can be applied to boost plant health and immunity to diseases like Phytophthora. However, good watering practices will be enough for the prevention.

Twig dieback can be caused by a few different fungal pathogens. Twig dieback usually occurs during the rainy season. Chemical treatment is not necessary. Simply prune off damaged twigs and branches to prevent the infection from spreading.

Huanglongbing (HLB) is also referred to as citrus greening disease. Symptoms of infection include yellow mottled leaves, sudden death in young trees, and small or deformed fruit. HLB is spread by the ACP, so controlling the insect will prevent the disease. It can also be transferred when grafting with infected plant material. There is no cure for HLB so once a tree is infected, it needs to be removed. Australian finger lime has shown some tolerance to HLB, so symptoms may be mild. If you suspect your tree is infected, it’s best to have it tested and removed if infected. Removing infected trees will prevent the spread to other citrus trees in the surrounding area. It is important to ensure that any new trees planted come from reliable nursery sources following each state’s regulations. For example, citrus trees grown in California should have a CDFA label that ensures they have come from clean nursery stock.

Frequently Asked Questions

Q: How long does it take for finger lime to fruit?

A: Finger lime will start to fruit after one year. They will produce an abundant amount of fruit after 4-5 years.

Q: Can you grow finger limes in the US?

A: Absolutely! Although it may be difficult to find in stores, there are a few online retailers that can ship a tree directly to your home.

Q: How big do finger lime trees get?

A: Australian finger lime trees range in size from 6-25 feet depending on the variety and rootstock. Trees can be pruned to maintain the desired height.


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