Citrus australasica (Finger Lime)

Common Name: Finger Lime (Caviar Lime)

Scientific Name: Citrus australasica

Plant Family: Rutaceae

Lifecycle: Perennial

The Australian finger lime is a unique citrus species prized for its “caviar-like” pearls that burst with tangy flavor. Growing Citrus australasica in Zone 8a is entirely achievable, especially with greenhouse protection where temperature, humidity, and airflow can be managed year-round. The plant's natural shade tolerance makes it particularly well-suited for protected cultivation, and its compact form is ideal for small spaces or specialty culinary orchards.

For in-depth guides and curated tools, be sure to check out our Recommended Books & Resources below.

Plant Profile

Characteristic	Information
Climate Suitability	USDA Zones 9–11 outdoors; Zone 8a with greenhouse protection; Köppen Csa/Csb
Sun / Shade Needs	Partial shade to filtered sun; avoids harsh midday heat
Watering Needs	Moderate; prefers consistent moisture but hates waterlogging
Soil Preferences	Well-drained, slightly acidic loam; pH 5.5–6.5
Spacing & Height	1.5–2 m spacing; typically 2–3 m tall (6–10 ft) in greenhouse conditions
Propagation Method(s)	Grafting preferred; also grown from seed (high variability)
Planting Timeline	Anytime in greenhouse; avoid winter planting outdoors
Companion Plants	Lemongrass, thyme, basil; avoid strong-rooted citrus competitors
Edible / Medicinal / Ecological Uses	Edible citrus “caviar,” garnishes, drinks, desserts; flowers attract pollinators
Pest / Disease Considerations	Susceptible to aphids and ant farming; scale possible in high humidity
Pruning / Harvest Notes	Light structural pruning; harvest when fruits soften and color deepens

Quick Plant Reference

• Care Level: Moderate

• Optimal Sunlight: Filtered sun or partial shade

• Water Needs: Moderate, even moisture

• Mature Size: 2–3 m (6–10 ft) tall; ~1.5 m (5 ft) spread

• Soil Type: Well-drained loam, slightly acidic

• Humidity: Medium

• Toxicity: Non-toxic to humans and pets

• Beneficial Pollinators: Bees, hoverflies

• Health Benefits: High vitamin C; antioxidant-rich vesicles

• Chilling Hours: Not required; frost-sensitive

• Pollination Requirements: Self-fertile

Our Citrus australasica Application @ Tough Kraut

Our finger lime started its life on the homestead in a pot after we bought it at a weekly market in 2023. Even before planting it into the soil, it gifted us a handful of fruits—proof that this species handles container life well. Once our greenhouse was completed in January 2024, we planted it directly into the ground to give the roots more freedom and stabilize humidity. The tree adapted quickly, producing small but steady harvests each year.

In 2025, we had our first pest challenge: aphids—with an enthusiastic ant team farming them for honeydew. We treated the tree with diluted cord soap in a spray bottle. After 3–4 treatments, the aphids (and their milkers) finally surrendered. The tree bounced back beautifully, offering a valuable lesson on greenhouse pest dynamics.

Step-by-Step Growing Guide

1. Choose the Right Site

Place the tree in a bright but indirectly lit location. Finger limes naturally grow under rainforest canopy, so filtered sunlight suits them well. If you notice leaf scorch or yellowing tips, the tree is likely receiving too much intense light.

2. Prepare the Soil

Use a slightly acidic, well-draining mix with compost and coarse sand. Pale or yellowing leaves often signal that soil pH has drifted too high, so citrus-specific fertilizer or a small amount of sulfur can help restore balance.

3. Plant the Tree

Set the plant slightly above grade to avoid waterlogging. In a greenhouse, be sure there is good airflow around the trunk and branches, since humid, stagnant air can encourage aphids and scale.

4. Water Consistently

Maintain steady moisture while allowing the top few centimeters of soil to dry between waterings. Irregular watering may lead to small or dropped fruit, while constant saturation stresses the roots.

5. Ensure Proper Pollination

Finger limes are self-fertile, but airflow and occasional gentle shaking of branches during bloom help increase fruit set. A few pollinators entering the greenhouse also improve results.

6. Prune Annually

Lightly shape the tree in late winter to maintain airflow and remove any deadwood. Finger limes fruit on new growth, but excessive pruning can delay the next crop, so keep cuts minimal.

7. Manage Pests and Diseases

Aphids and ants are the most common issue in greenhouse-grown finger limes. Early intervention with diluted soap spray or neem oil keeps populations in check. On our homestead, cord soap required several rounds to fully break the ant–aphid cycle.

8. Harvest and Store

Harvest when fruits soften slightly and reach full color. Store in the fridge for up to two weeks. The citrus “caviar” vesicles stay freshest when the fruit is only opened right before use.

9. Note

Finger limes often produce small fruits, even under ideal conditions. These miniature limes contain the highest-quality vesicles, so size isn’t an indicator of poor tree health.

Kraut Crew Insight

Our finger lime has become one of our most rewarding greenhouse experiments—compact, productive, and full of character. Watching those tiny citrus pearls form inside the leathery fruits feels like a small miracle every season. And after our battle with aphids, we now know: even exotic citrus behaves predictably when you slow down, observe, and respond early.

Photos

November 27, 2025

November 27, 2025

November 27, 2025

Herman’s Tough Kraut Field Notes: Solving Finger Lime Cultivation Challenges

Growing finger lime in a Mediterranean greenhouse comes with its own set of puzzles. In this troubleshooting and FAQ section, we take a practical look at airflow, pests, watering, and fruiting patterns—based on our own hands-on experience.

Finger limes may appear delicate, but once established they’re resilient. The biggest issues tend to be related to confined greenhouse microclimates: stagnant air, humidity spikes, and opportunistic pests like aphids. Many of the most common “What’s going on?” questions from readers actually match situations we’ve encountered ourselves.

Q: My finger lime has aphids every spring. What’s the best organic treatment?

A: Use diluted soap sprays (like cord soap) every 3–5 days until colonies collapse. Eliminate ants with sticky bands or soil-safe repellents to stop honeydew farming.

Q: The leaves look yellowish and thin. Help?

A: Likely pH or nutrient imbalance. Finger limes are sensitive to high pH; apply a citrus fertilizer with micronutrients.

Q: Fruits are forming but dropping prematurely. Why?

A: Inconsistent watering or heat spikes. Maintain even soil moisture and increase shade during heatwaves.

Q: Branches seem brittle. Is this normal?

A: Yes—finger limes have naturally wiry, thorn-covered branches. Support heavier fruiting limbs if needed.

Q: Should I mist the greenhouse for humidity?

A: Only lightly. Too much humidity invites aphids and scale. Prioritize airflow rather than misting.

Recommended Books & Resources

Books

• Growing Citrus: The Essential Gardener’s Guide by Martin Page

  A practical and approachable handbook covering citrus biology, pest control, pruning, and container/greenhouse cultivation, making it ideal for growers experimenting with specialty citrus like finger lime in Zone 8a.

• Citrus: Complete Guide to Selecting & Growing More Than 100 Varieties by Lance Walheim

  One of the most authoritative citrus guides for home growers, offering detailed variety descriptions, troubleshooting tips, and climate-specific advice for Mediterranean regions and protected growing environments.

• Uncommon Fruits for Every Garden by Lee Reich

  A celebration of rare and specialty fruits, including cultivation advice for lesser-known species like finger lime, perfect for readers expanding their homestead orchard beyond the mainstream.

• Growing Tasty Tropical Plants in Any Home, Anywhere by Laurelynn G. Martin & Byron E. Martin

  A greenhouse-friendly guide focused on tropical and subtropical fruit trees, with clear instructions on managing humidity, light, and soil — all essential for successfully growing Australian finger lime indoors or under cover.

Resources

• Premium Australian Finger Lime Soil Mix

  A specialty soil blend engineered for finger limes, providing the acidity, drainage, and aeration this species needs to thrive in pots or greenhouse beds.

• Neem Bliss 100% Cold-Pressed Neem Oil Concentrate

  A reliable, organic, go-to solution for controlling aphids, mites, and scale on greenhouse citrus, especially helpful for avoiding chemical treatments in enclosed spaces.

• Gideal Dual-Sided Yellow Sticky Traps (20-Pack)

  A simple but highly effective tool for catching flying pests like whiteflies and fungus gnats, helping growers detect issues early and maintain pest-balanced greenhouse conditions.

• Tough Kraut Resources

  Our curated list of tools, organic sprays, and homestead-growing essentials.

Entry last updated: 2025-12-09

This post is part of the Tough Kraut Plant Library, documenting what really grows on our off-grid homestead in Central Portugal.