Australian finger lime is a thorny variety related to the citrus family, that produces delicious lemons that are very sought after by great culinary chefs.
Australian Finger lime facts
Name – Microcitrus australasica
Height – 3 to 10 feet (1 to 3 m),
20 feet or 6 meters if unpruned
Exposure – full sun
Stock type – grafted
Soil – well-drained
Foliage – evergreen
Flowering – March to July
Harvest – November to March
Planting Australian finger lime
It is only possible to plant Australian finger lime in the ground in mild-wintered areas because they can’t survive freezing temperatures and strong frost spells can be fatal to them.
- They need full sun to bear fruit.
- They like well drained soil.
- Keep them out of the wind.
- Occasional light frost is possible but not wished for.
- Being crowded by other trees or plants with developed root systems like banana trees hinders their growth.
In colder areas, plant your Australian finger lime in pots.
Repotting your Australian finger lime
Potted Australian finger lime cannot extract the nutrients they need from the ground.
So the pot and soil you have put in it are their only source of food for them to stock up and grow.
Re-potting is thus critical.
- Re-potting takes place every 2 or 3 years in spring.
- Choose high-quality citrus-specific or planting soil mix.
- Double-check that the bottom of the pot has a hole drilled in.
- Place a bed of small pebbles or clay marbles at the bottom of the pot to ensure excellent drainage.
Potted Australian finger lime trees in winter
Growing Australian finger lime trees in pots is most adapted. This makes it possible to bring the citrus trees to a well-lit spot where it doesn’t freeze in the winter.
Australian finger lime trees aren’t indoor plants, and can’t bear staying in a heated environment all year round. They need relatively lower temperatures from October to May.
It is important to place them in an unheated greenhouse for instance, where the temperature never drops below 32°F (0°C).
- If you’re looking for citrus plants that cope well with growing indoors, check out calamondin trees.
Pruning and caring for Australian finger lime trees
When pruning finger lime trees, wear gloves to protect your hands, because their thorns are very prickly.
- Note: these thorns may also damage fruits in windy areas. Snip nearby thorns off if you want to protect a few specific fruits.
- Best is to build a wind barrier around the tree.
- Do the heaviest pruning right after the harvest.
Shoots should be pruned off every year. That way, fruits benefit from the greatest amount of sap. Aim for a regular, harmonious shape that is easy to harvest.
Remove dead wood regularly and clear the inside branches of your Australian finger lime to let light penetrate to the center.
- More on how to prune finger lime
Watering your Australian finger lime tree
In pots, Australian finger lime trees dry up much faster than if they were planted in the ground, so it is essential that they be watered regularly.
In summer, frequent watering is required, whereas watering can be reduced in winter.
- Water as soon as the soil is dry, without flooding the pots.
- Avoid all heat sources such as nearby radiators, because this could dry your tree out.
Every two weeks, during the growth phase, add citrus-specific fertilizer to boost fruit-bearing.
Check our video with expert guidance on Australian finger lime trees
Flowering, fruiting & harvesting finger lime
After 3 to 5 years, young trees will start bearing flowers. The harvest increases significantly after 2 years of fruit-bearing.
Usually trees are from grafted stock to make sure they grow and bear expected fruits.
- Citrus finger lime grown from seed takes longer to bear flowers and fruits (4-6 years).
- Fruit from seed-grown plants may not turn out as expected due to cross-pollinating from other citrus trees.
- Not all finger lime varieties produce seeds in their fruits, these are seedless varieties.
Fruit set for Australian finger lime
In the very best conditions, only 60 to 70% of flowers will “set” or start turning into fruits.
Pollination is normally the work of bees and other insects.
- Honeybees, certain types of flies and even predator pests such as beetles all take a part in pollinating flowers. Set up a hive in your garden and an insect hotel to attract them!
- It’s possible to hand-pollinate flowers delicately to try and trigger fruit formation.
To hand pollinate finger lime, a small paintbrush with soft strands is needed:
- simply swipe the brush delicately around the inside of each flower, one after the other
- you should notice pollen caught in the brush hairs, like dust
- some flowers may be at different stages of maturity, so this may need to be repeated every few days or weekly as new flowers appear
Finger lime fruit drop
Keeping the soil around the tree slightly moist is essential to reduce fruit drop.
- Plant mulch, especially seaweed-based mulch, will do the trick.
- It also breaks down into much-needed nutrients and trace elements.
- Water up to twice a week, especially for potted specimens.
However, it is normal for a certain amount of fruits to drop. Abundance is nature’s way of sharing to other species while still ensuring reproduction. It’s common to see up to half of set fruits start dropping.
- Apart from water stress mentioned just above, a relevant cause of fruit drop is lack of trace elements in soil. This is common in pot-grown finger lime.
- Fertilizing with citrus-specific fertilizer or fermented tea made from weeds can counter these deficiencies.
Harvesting finger lime
Harvest season is usually November to March. Depending on variety and growing conditions, it can take up to 10 months for a finger lime fruit to ripen.
- Wait for the fruits to easily break off the branch with a light twist or tug.
- They won’t mature when separated from the tree.
- Young trees bear smaller fruits than older ones.
- Better use small, stackable boxes instead of large baskets in order to not crush the delicate fruits.
You will ensure the finger limes mature best by protecting the tree from freezing.
An adult tree, properly pruned, can produce up to 45 lbs (or 20 kg) of fruit a year.
Finger lime fruit color
Finger lime fruits come in many colors, sometimes even different colors on the same tree!
From wasabi-like green to ruby red to pearl white and purple, it’s a wonder this fruit is only mostly known in restricted circles!
Of all the citrus varieties, the finger lime family has the most colorful and varied fruits.
Diseases commonly found on Australian finger lime trees
- European brown rot – lemons rot while still on the Australian finger lime tree
- Melanose – a fungal disease that attacks leaves, twigs and fruit
- Scale insects – whitish masses colonize leaves and sometimes fruits
- Aphids – leaves curl up and fall off
- Katydids and grasshoppers often feed on the fruit
- Psyllids are another pest that can be found on leaves
- Thrips – usually attack fruits in shaded portions of the tree. Fruit is still perfectly edible, but skin is spotted and not so appealing.
Luckily, the common fruit fly isn’t carried on finger lime. This makes it possible to export it to new countries without fearing contamination by fruit fly. However, much care must be given regarding the invasive citrus gall wasp.
Citrus gall wasp
This tiny wasp only a few millimeters long lays eggs in fresh shoots. They commandeer growth of the branch to form a gall and then hatch. This pest is currently only found in Australia, although possible sightings in New Zealand indicate it may be spreading further. The best way to deal with it is to prune out gall-infected branches before any adult citrus wasp hatches.
Australian finger lime is actually the original host for citrus gall wasp. However, when planted with other non-native citrus, it will prefer laying on lemon, grapefruit, and mandarin citrus trees instead. Having been exposed to the parasite for longer, the native tree has developed a somewhat higher defense mechanism. Indeed, not all eggs and larvae on an Australian finger lime are able to reach maturity.
Branches grow in random directions, mostly from lower trunk
Citrus is vulnerable to loss of apical dominance. New shoots come from lower trunk upon pruning, instead of branching out from the tip of the tree. This results in a hard to train tree that is more vulnerable to disease. It is the result of insufficient availability of boron trace elements.
Cooking with finger lime fruit
When ripe, each finger lime fruit contains hundreds of kernel-sized crystals under pressure under the skin. Upon slicing the fruit, these juicy beads burst out and are ready to nibble or eat directly!
Just like real caviar, each bead will wait until you bite it to release the juice inside. You can sprinkle a little sugar on it to reduce the tartness if need be.
What to cook with finger lime
It is perfect as a wonderful decoration to many dishes, topping for salads, or added on Tex Mex foods, too!
They’re also excellent paired with seafood, to replace the usual sliced lemon on oysters and seashells. Amateurs of sushi will love adding it as a delicious variation. Spread them across grilled fish to hydrate with a delicious touch. Also great with poultry and white meats.
You can pickle the entire fruit, especially for smaller varieties.
Cocktails with finger lime are also a real treat.
Finally, when blended or pressed, the juice works wonders in tarts, ice cream, and flans of all types.
The peel is also edible, like that of kumquat, though not as soft. Use it to replace lemon zests in many recipes for a new delicious experience.
Keeping finger lime
Fruits will keep for up to a month if kept in the refrigerator.
It’s also possible to freeze them whole, but you won’t get the same texture as fresh ones. Incorporate them in Asian soups or noodles, jams, and other recipes where taste is more relevant.
Learn more about Australian finger lime
Their juice is trapped in tiny capsules that look like pearls, and burst in the mouth, releasing an explosion of flavors like lemon, citrus and grapefruit: this is the “lime caviar” that great chefs crave!
Finger lime native habitat
This special citrus evolved as a shrub in Australian rain forests (Queensland and New South Wales to be exact). Though part shade is the natural tropical habitat, in temperate climates full sun is needed or it won’t bear fruit well.
Thanks to cross-pollination and diverse growing conditions, a great many varieties exist. Most of them are still awaiting discovery. Wild finger lime trees are often genetically quite different from each other.
Smart tip about finger lime
Pick the finger limes when they easily break off from their branch. Before that, they’re very bitter.
Finger lime on social media
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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Open finger lime fruit (also on social media) by Gastronomia Slow under © CC BY 2.0
Mealy bugs on finger lime tree by Scot Nelson ☆ under Public Domain
Ripe finger lime on tree by Malcolm Manners under © CC BY 2.0
On social media: Fresh pink finger lime fruit by Eric Weisser under © CC BY-SA 2.0