Australian Finger Lime
Australian Finger Lime tree overview:
Australian Finger Lime are unique fruit that come from a hearty tree.
Australian Finger Lime fruit appearance:
As you might expect, Australian Finger Lime fruit are shaped a bit like fingers. However, on closer inspection, I think they look more like miniature zucchinis.
The fruit range in size from as small as an inch long to as much as 12 cm in length. This difference in size may be related to the particular cultivar, age/health of the tree and/or local environmental factors. Much like other fruit trees, thinning of large fruit clusters may improve fruit size.
Depending on the variety of fruit, the color of the outside-skin ranges from green to red and purple to almost black. Because finger lime trees are naturally very thorny, the skin of the fruit may be easily damaged by their thorns and wind rub. However, this is more of a cosmetic issue than anything because superficial abrasions don’t seem to affect the fruit taste.
The texture of the flesh is really unique. The caviar like vesicles (sometimes called crystals) of the fruit seem to be packed-in under pressure. When fresh fruit is opened, the tiny vesicles typically spill out of the casing.
Those caviar like vesicles come in a wide range of colors ranging from green, white, yellow, purple, pink and bright red. I have even heard of a blue fleshed variety.
Some trees will also bear fruit with different colors of vesicles in each fruit. For example, I have a tree that bears fruit with white, pink and/or pink reddish vesicles. For those varieties of trees, you can’t tell what color the flesh of the fruit will be… “Its like a box of chocolates.”
The recent popularity of the fruit had prompted investment in genetic crosses and improved selections which are currently under development. More colors and sizes to come.
Australian Finger Lime taste:
The wonderful uniqueness of this fruit comes from the caviar like texture of the flesh. These multiple small round vesicles are a stunning gustatory experience. If you have ever had a “California Roll” with fish eggs on it… well the fruit vesicles are lot like those eggs.
The fruit is tart/acid – on the same level of a typical lime. However, the total flavor is not exactly like a lime. There more of a floral element to the flavor. Sometimes, the fruit almost tastes like an unsweetened “Sweet Tart” candy.
The Australian Finger Lime is gaining popularity among creative chefs and curious foodies. The bright flavor of the “lime caviar” fruit seems to be a natural fit as a seafood garnish.
I have tried to add it to drinks, but unfortunately the vesicles basically sink to the bottom of the glass resulting in an intense tart surprise at the end.
Surprisingly, even though it is a powerful flavor, many like to eat the fruit raw (including myself). Adding sugar makes the fruit taste like sweet-tart candy.
I have also heard that the finger lime peel can be dried and used as a flavoring spice… although I have not tried that.
Australian Finger Lime fruit season:
In California the flowers seem to have a prolonged bloom cycle and I have seen them mainly from April to August. However, I have seen flowers as late as October. I have been picking ripe fruit from May to November.
Like other citrus, finger lime fruit must be fully ripe when picked because they do not ripen off the tree. Unripe fruit will be bitter.
The easiest way for me to tell if the fruit are ripe, is to give a gentle tug. If the fruit detach easily then they are probably ready. Others have written that the fruit “feel full” when they are ripe but I don’t exactly know what that means. Other than the obvious tasting of the fruit, another way to confirm ripeness is to split the fruit open and then gently squeeze. If the fruit is ripe, the vesicles should come out separately and freely.
Grafted finger lime trees may begin fruiting at 3 years of age, but larger quantities of fruit are usually seen around 6 years of age.
Australian finger limes typically have dense foliage with multiple small leaves. Therefore, they may provide some privacy if planted strategically. The trees also have many small thorns, so they are not the best option for the border of walkways or in high traffic areas.
Different finger lime tree cultivars have a variety of shapes and sizes. Some finger lime trees can grow as tall as 6 meters in the wild. Try to get as much info as you can about the particular growth habitat of your finger lime so you can best optimize your landscape.
The Australian government has a document that outlines the characters of several different varieties:
- Citrus australasica ‘Alstonville’ – a tall growing shrub producing dark green-black fruit with a pale green flesh.
- Citrus australasica ‘Blunobia Pink Crystal’ – a compact medium shrub producing green-brown fruit with a deep pink flesh.
- Citrus australasica ‘Durhams Emerald’ – a medium open shrub producing black fruit with an emerald green pulp.
- Citrus australasica ‘Judy’s Everbearing’ – a tall shrub producing green-brown to maroon fruit with a green to dark pink flesh
- Citrus australasica ‘Pink Ice’ – a medium growing shrub producing reddish maroon fruit with a clear to pink flesh
Reference: Growing Australian native finger limes
I have read that Australian Finger Lime trees are slow to establish and may show little sign of any growth for the first year after planting.
However, this is definitely not my experience. For example, I received a potted finger lime tree as a gift from a friend. That tree was so root bound that there was basically no soil left in the pot. This particular plant was in one of those beautiful painted curvy ceramic pots and I wanted to extract the tree without breaking the container… so I could give the container back to my friend. Therefore, I was forced to sacrifice a lot of the peripheral roots to free the roots from the confines of the vessel. (Note, in my extraction, I was otherwise very gentile and cautious to keep the core root ball intact).
From there I just followed my typical planting process. To my delight, the tree almost immediately started putting out new growth.. and now a year later the tree is over twice the size it was at the initial planting. Therefore, at least from this experience, this plant seem much heartier than your typical citrus.
Similar to lemons the leaves are dark purple when young and turn green as they mature.
The flowers are rather tiny and are only really appreciated on close inspection. Therefore, this is not a “showy” plant. In fact, the numerous dark sausage-like fruit hanging on the tree is not exactly ornamental. However, a tree full of fruit is a bit of a conversation piece, especially if you have friends that can appreciate the unusual.
In its natural habitat, finger lime trees grow on a wide range of soil types.
However, I suspect they will be a lot happier if you give the soil some extra love. Therefore, I do what has worked for all of my other trees; I aggressively augmented the soil with grow mulch/compost, and inoculate the roots with Micorriza. Note, the soil must be well draining with these guys. Click here for the planting method that I have used with great success.
Australian finger limes are said to be drought tolerant. Regardless, I water most of my citrus trees the same… which means I schedule deep watering around 2x (sometimes 3x) a week in the summer (after they are established).
For established trees, I cut way back on the watering in the winter… mainly because winter is usually our wet season in California and you can get away with not watering.
Covering the ground around the base of the tree with a nice layer of wood mulch will help to retain moisture in the summer and help to keep the roots cool.
In their natural habitat, Australian Finger Lime trees typically grow as an understory shrub or tree. Therefore, they are built to grow in the shade. However, they also seem to do great in full sun and this is how most commercial growers plant them.
I have not seen any specific research on finger lime nutrient requirements. None the less, finger limes seem to need a lot less fertilizer than other commercial citrus varieties. Many growers are using only about 25–30% of the total annual amount of fertilizer used for other citrus varieties.
To prevent fruit abortion, some have recommended avoiding fertilizer from the time of flowering to the point when the fruit are 1 cm long. Others have reported that over fertilization can cause limb dieback. I have not noticed any of this.
Otherwise, I try to fertilize all of my citrus trees from late winter to mid-summer. The rational is that I don’t want to encourage young leaf growth in the winter because of the risk of cold damage to the susceptible young leaves. On the other end, I don’t want to encourage excessive young growth during leaf miner season which starts around July.
I generally use a balanced fertilizer such as 15-15-15 on my citrus and apply it in 4 doses during the fertilization season described above. I also give a single dose of citrus specific micronutrients in the spring. I have been trying different brands of citrus micronutrient fertilizer, but this organic one with a money back guarantee sold on Amazon looks really great.
Lately I have also been adding in all kinds of other goodies as a top dressing over the root zone such as mushroom compost; grow mulch, worm castings, etc. I am getting the sense that citrus like the variety. See my earlier post for how to get free compost.
When it comes to temperature, I am not aware of any specific research on finger limes. However, I would basically treat them like other citrus in this regard. Plant them in a warm sunny location and try to avoid areas with extreme hot or cold winds. They are likely able to tolerate a light frost, but that is just my conjecture.
In general, just about any citrus will freeze when the temperature drops below 27-28°F.
In my years in San Diego, frost protection for my citrus has not been necessary. Sure, they dont like the cold, but they get by without any special care. However, cold/frost protection is very important in cooler climates.
For more information about the lowest temperatures that you can expect in your specific area, check out my article “Climate Zones: What can I grow in my yard?”
The flowers of finger lime trees seem to be a bit small for bees. Perhaps other insects or wind play a greater role in pollination of these flowers. Regardless, curved/deformed fruit are likely the result of poor pollination.
Most finger lime trees that you would buy are grafted. The trees grown from seed have unpredictable (not necessarily true to type) fruit quality. In addition, seed grown finger limes may be slower growing and can take longer to bear fruit.
Finger limes are susceptible to most of the same pests and diseases as other citrus.
A common disease reported to affect finger limes in Australia is melanose (Diaporthe citri). This is a fungal disease that causes dark brown to black spots on the foliage, twigs and fruit. Spores of the fungus develop in dead citrus tissue and are released by water and/or rainfall. The fungus affects all citrus varieties and the incidence of melanose usually increases as trees age and the amount of dead wood in the canopy increases.
On the positive side, finger limes are reported to be highly resistant to Phytophthora citrophthora root disease.
The major pest for all of my citrus is the Citrus Leafminer. Click here to see my post about the diagnosis and treatment of Citrus Leafminer.
One of the most important things to do is to keep the ants out of the tree which often bring aphids, scale and mealybugs with them. A great way to do this is to use Tanglefoot. However, don’t apply Tanglefoot directly to the bark because the thin bark of citrus can be easily damaged this way. Create a skirt of masking tape around the trunk of the tree (with the sticky-side out) or buy the Tanglefoot guard paper wrap. Then add the Tanglefoot on that skirt/paper.
Citrus Greening AKA Huanglongbing (HLB) is currently wreaking havoc in Florida. All citrus growing states are on high alert and most are under quarantine. The disease is incurable and will usually kill a tree within several years. The disease is spread by the insect known as the Asian Citrus Psyllid. Leaves with HLB disease have a blotchy yellow pattern that is not the same on both sides of the leaf. If you suspect this disease, it should be reported to the California Department of Food and Agriculture hotline at 1-800-491-1899.
Like Tahitian limes (AKA Bearss limes), finger limes are reported to occasionally suffer from stylar end breakdown (SEB). This is not really a disease but can be annoying. I wrote more about this process in this article on Bearss limes.
- According to the “Swingle system” of taxonomy the finger lime is not part of the genus citrus, but in a related genus Microcitrus.