Origin and Common Names
Citrus australasica F. Muell. is a small tree or shrub that belongs to the Rutaceae family. It is also known as finger lime, Australian finger lime, lime caviar, and caviar lime. The plant is native to the rainforests of Australia, specifically in the border region of Queensland and New South Wales.Uses
The fruit of Citrus australasica F. Muell. is highly valued for its juice vesicles that resemble caviar. These vesicles are commonly used as an exclusive garnish in gourmet dishes, cocktails, and desserts. The tangy and acidic taste of the lime caviar perfectly complements seafood, sushi, salads, and other dishes. Additionally, finger lime leaves are used in traditional medicine for treating skin diseases, headaches, and rheumatism.General Appearance
Citrus australasica F. Muell. is a small tree or shrub that can grow up to 20 feet tall. The plant has a bushy growth habit and is characterized by numerous thorny branches that can grow dense and intertwined. The leaves of the finger lime are elliptic, glossy, and dark green. The flowers are white and fragrant, and the fruit of the plant is oblong in shape with a thin rind that varies in color from green to maroon. The pulp of the fruit consists of tiny, round juice vesicles that are transparent and resemble caviar. The fruit of Citrus australasica F. Muell. is usually harvested in winter and early spring.Light Conditions
Citrus australasica F. Muell. requires bright light for optimal growth. It can tolerate partial shade, but insufficient light can lead to sparse foliage and poor fruiting. Exposure to direct sunlight should be limited, especially during the hottest parts of the day, as it can cause leaf scorching. It is therefore best suited to a location where it can receive bright, filtered light.
Temperature Requirements
This plant is native to the eastern parts of Australia and thrives in subtropical and tropical climates. Therefore, it prefers warm temperatures between 60°F and 85°F (16°C–29°C) for optimum growth. Temperatures below 50°F (10°C) can cause damage to the plant, and frost can be fatal. In colder climates, it is advisable to plant in pots that can be moved indoors during the winter.
Soil Requirements
Citrus australasica F. Muell. grows best in well-drained soils that are acidic to slightly alkaline (pH 5.5–7.5). The soil should be rich in organic matter and high in nutrients, particularly nitrogen, phosphorus, and potassium, for healthy growth and fruit development. To improve drainage, it is recommended to mix the soil with perlite or sand. Additionally, regular fertilization with a balanced fertilizer formula can help ensure that the plant gets the nutrients it needs to thrive.
Cultivation Methods
The Citrus australasica F. Muell., also known as finger lime or caviar lime, is a small thorny tree that can grow up to six meters in its native rainforest habitat. Growing this plant from a seed can take up to seven years to mature, so it’s recommended to start with seedlings bought from a reputable nursery. The tree thrives in warm temperatures and is sensitive to frost, making it ideal for growing in sub-tropical and tropical regions with well-drained soil.
Watering Needs
Caviar lime trees require regular watering to keep the soil moist but not waterlogged. During hot weather, it’s crucial to keep the soil moist to avoid the tree dropping its fruit. Overly dry soil can lead to leaf drop and poor fruit production. Generally, the tree should be watered at least once a week, and more frequently during a heatwave.
Fertilization
Citrus trees require regular fertilization to thrive and produce fruit. Apply a citrus-specific fertilizer that contains nitrogen, phosphorus, and potassium to the soil around the tree regularly. The ideal time to fertilize is during the tree's active growth period in early spring and again in early summer. When applying fertilizer, do not let it touch the trunk or foliage, as it can damage the plant.
Pruning
Pruning is essential for maintaining the tree's shape, removing dead or diseased branches and promoting new growth. The best time to prune a caviar lime tree is in late winter before its active growth phase. Always use clean, sharp pruning tools and cut back to just above a healthy bud or lateral branch. Pruning should be kept to a minimum to avoid reducing the fruit yield.
Propagation methods of Citrus australasica F. Muell.
Citrus australasica F. Muell. is commonly propagated through seeds, cuttings, and grafting or budding.
Seed propagation
Seeds must be carefully harvested from mature fruits and washed thoroughly with water to remove any remaining pulp. It is recommended to use freshly harvested seeds, as older seeds may have reduced viability.
Before sowing, soak the seeds in water for 24 hours to soften the seedcoat and increase germination rate. Sow the seeds in well-draining, moist soil and cover them with a thin layer of sand, vermiculite, or peat moss. Keep the soil moist but not waterlogged and ensure that the seeds receive direct sunlight or bright, indirect light.
Germination can take 2-4 weeks, after which seedlings can be transplanted to individual pots or directly into the ground.
Cutting propagation
Cuttings may be taken from mature, healthy branches in early spring or late summer. Use a sharp, sterilized knife to take cuttings that are 4-6 inches long and have at least two nodes. Remove any leaves from the lower half of the cutting.
Dip the cut end of the cutting into rooting hormone powder and plant it in a well-draining potting mix. Water the cutting well and cover it with a plastic bag or dome to retain moisture and humidity. Place the cutting in a bright but shaded area and keep the soil moist but not soggy.
The cutting should start to root within 4-6 weeks. Once roots have formed, the cutting can be transplanted to a larger pot or directly into the ground.
Grafting or budding
Grafting or budding is a common propagation method for Citrus australasica F. Muell. and can be used to maintain desirable fruit-producing traits. It involves joining the desired scion (the fruit-producing portion of the plant) with a hardy rootstock.
Grafting should only be done by experienced grafters and may involve several techniques, such as whip grafting, cleft grafting, or bud grafting.
Budding is a simpler technique that involves inserting a single bud from the desired scion into a rootstock. This technique is commonly used in commercial citrus production.
Disease Management for Citrus australasica F. Muell.
Citrus australasica F. Muell., commonly known as finger lime, is susceptible to various diseases that can affect its growth, yield, and overall health. Proper disease management strategies must be implemented to prevent the occurrence and spread of diseases. Below are some common diseases that might affect finger lime and ways to manage them.
Phytophthora Root Rot
Phytophthora root rot is a soil-borne disease caused by the fungus Phytophthora citrophthora. It can cause yellowing and wilting of leaves, defoliation, and even death of the plant. The disease can be managed by planting resistant cultivars, avoiding waterlogging, improving soil drainage, and applying fungicides such as mefenoxam.
Citrus Canker
Citrus canker is a highly contagious bacterial disease caused by Xanthomonas campestris pv. citri. It can cause leaf spotting, stem cankers, defoliation, and reduced fruit quality. The disease can be managed by removing and destroying infected plants, avoiding overhead watering, improving air circulation, and applying copper-based fungicides.
Citrus Scab
Citrus scab is a fungal disease caused by Elsinoë fawcettii. It can cause scabby lesions on fruit and leaves, reducing their appearance and marketability. The disease can be managed by applying copper-based fungicides during the flowering period, removing fallen leaves and fruit, and using resistant cultivars.
Pest Management for Citrus australasica F. Muell.
Finger lime can also be affected by various pests that can cause damage to the plant and reduce its yield. Proper pest management strategies must be implemented to prevent pest infestations. Below are some common pests that might affect finger lime and ways to manage them.
Citrus Leafminer
Citrus leafminer is a small moth that can cause twisting and distortion of leaves, reducing their photosynthetic efficiency. The pest can be managed by pruning affected leaves, using sticky traps to monitor adult moths, and applying insecticides such as spinosad.
Citrus Flatid Planthopper
Citrus Flatid Planthopper is a sap-sucking insect that can cause yellowing and wilting of leaves, stunting of growth, and fruit deformation. The pest can be managed by removing infested leaves, improving air circulation, and applying insecticides such as imidacloprid.
Fruit Fly
Fruit fly is a common pest that can cause fruit damage and premature drop. The pest can be managed by using bagging or netting to cover the fruit, applying insecticides such as spinosad, and using pheromone traps to monitor adult flies.
