Citron
Citrus medica
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The citron (Citrus medica) is a large, fragrant citrus fruit and one of the original citrus species from which all other cultivated citrus types are derived through natural hybridisation or selective breeding. It is a slow-growing shrub or small tree in the family Rutaceae, cultivated since antiquity for its thick, aromatic rind, which is used in perfumery, confectionery, and religious rituals.
Taxonomy
Kingdom
Plantae
Phylum
Tracheophyta
Class
Magnoliopsida
Order
Sapindales
Family
Rutaceae
Genus
Citrus
Species
Citrus medica
The citron is believed to have originated in the foothills of the Himalayas, in a region encompassing north-eastern India, northern Myanmar, and China's Yunnan province.
• One of the earliest citrus fruits to be cultivated, with evidence of its presence in Mesopotamia dating back to around 4000 BCE.
• Introduced to the Mediterranean region via Persia (hence the species name 'medica') by the armies of Alexander the Great around 300 BCE.
• Theophrastus referred to it as the 'Median apple' or 'Persian apple'.
• One of the earliest citrus fruits to be cultivated, with evidence of its presence in Mesopotamia dating back to around 4000 BCE.
• Introduced to the Mediterranean region via Persia (hence the species name 'medica') by the armies of Alexander the Great around 300 BCE.
• Theophrastus referred to it as the 'Median apple' or 'Persian apple'.
The citron is an evergreen shrub or small tree, typically growing 2.5 to 5 metres tall, with irregular, straggling branches and long spines in the leaf axils.
Leaves:
• Alternate, oblong to elliptic, 8–20 cm long, with serrated margins.
• Distinctly aromatic when crushed; petioles are not winged or only very narrowly winged, unlike many other citrus species.
Flowers:
• Large, white or purplish on the outside, fragrant, and usually perfect (containing both male and female parts).
• Buds are often tinged with a deep reddish-purple hue.
Fruit:
• A large, oblong or irregularly shaped hesperidium, 15–30 cm long.
• Rind is extremely thick (often constituting 50–70% of the fruit's volume), bumpy, and bright yellow when ripe.
• Flesh is pale greenish-yellow, firm, dry, and acidic to mildly sweet, with a small central core.
• Seeds are numerous, smooth, and pointed at one end.
Leaves:
• Alternate, oblong to elliptic, 8–20 cm long, with serrated margins.
• Distinctly aromatic when crushed; petioles are not winged or only very narrowly winged, unlike many other citrus species.
Flowers:
• Large, white or purplish on the outside, fragrant, and usually perfect (containing both male and female parts).
• Buds are often tinged with a deep reddish-purple hue.
Fruit:
• A large, oblong or irregularly shaped hesperidium, 15–30 cm long.
• Rind is extremely thick (often constituting 50–70% of the fruit's volume), bumpy, and bright yellow when ripe.
• Flesh is pale greenish-yellow, firm, dry, and acidic to mildly sweet, with a small central core.
• Seeds are numerous, smooth, and pointed at one end.
Citron trees are highly sensitive to environmental extremes and require specific conditions to thrive.
• Thrive in subtropical to warm temperate climates; less cold-hardy than most other citrus species, with damage occurring below -2°C.
• Prefer deep, well-drained, slightly acidic to neutral soils (pH 5.5–7.0).
• Intolerant of waterlogged conditions, which can lead to root rot (Phytophthora spp.).
• High susceptibility to pests common to citrus, including scale insects, mealybugs, and citrus leaf miner.
• Thrive in subtropical to warm temperate climates; less cold-hardy than most other citrus species, with damage occurring below -2°C.
• Prefer deep, well-drained, slightly acidic to neutral soils (pH 5.5–7.0).
• Intolerant of waterlogged conditions, which can lead to root rot (Phytophthora spp.).
• High susceptibility to pests common to citrus, including scale insects, mealybugs, and citrus leaf miner.
The edible flesh of the citron is not typically consumed fresh due to its dry texture and high acidity.
• The primary nutritional value lies in the thick rind, which is rich in dietary fibre, vitamin C, and various bioactive compounds including flavonoids and essential oils.
• Candied citron peel is a source of sugar and carbohydrates.
• The primary nutritional value lies in the thick rind, which is rich in dietary fibre, vitamin C, and various bioactive compounds including flavonoids and essential oils.
• Candied citron peel is a source of sugar and carbohydrates.
The fruit is non-toxic to humans. However, as with many citrus species, the peel contains high concentrations of essential oils (e.g., limonene) and psoralens, which can cause phototoxic reactions in sensitive individuals upon skin contact followed by sun exposure. The seeds and other plant parts may contain compounds that are mildly toxic to domestic pets if ingested in large quantities.
Cultivating citron requires patience and attention to frost protection and pruning.
Climate:
• Best suited to USDA hardiness zones 9b–11.
• In cooler regions, it can be grown in large containers and overwintered in a bright, cool greenhouse or conservatory.
Light:
• Full sun for optimal fruit development and rind quality.
Soil:
• Requires loose, fertile, and well-drained soil.
• A recommended mix for containers is a high-quality cactus and citrus potting mix amended with additional perlite.
Watering:
• Water deeply and regularly during the growing season, allowing the top few centimetres of soil to dry out between waterings.
• Reduce watering significantly in winter to prevent root rot.
Pruning:
• Prune to maintain shape, remove dead or crossing branches, and control the long, vigorous water sprouts characteristic of the species.
• The thorny nature of the branches requires care when handling.
Propagation:
• Typically propagated by cuttings to maintain varietal characteristics, as seed-grown trees may exhibit variability.
Climate:
• Best suited to USDA hardiness zones 9b–11.
• In cooler regions, it can be grown in large containers and overwintered in a bright, cool greenhouse or conservatory.
Light:
• Full sun for optimal fruit development and rind quality.
Soil:
• Requires loose, fertile, and well-drained soil.
• A recommended mix for containers is a high-quality cactus and citrus potting mix amended with additional perlite.
Watering:
• Water deeply and regularly during the growing season, allowing the top few centimetres of soil to dry out between waterings.
• Reduce watering significantly in winter to prevent root rot.
Pruning:
• Prune to maintain shape, remove dead or crossing branches, and control the long, vigorous water sprouts characteristic of the species.
• The thorny nature of the branches requires care when handling.
Propagation:
• Typically propagated by cuttings to maintain varietal characteristics, as seed-grown trees may exhibit variability.
The citron is primarily cultivated for its aromatic rind, not its flesh.
• The thick, fragrant rind is candied and used as a key ingredient in fruitcakes, panettone, and other rich baked goods.
• The essential oil, extracted by cold-pressing the rind, is a prized component in high-end perfumery and aromatherapy.
• The fruit holds significant religious and ceremonial importance in the Jewish festival of Sukkot, where a specific, unblemished variety known as the 'etrog' is used.
• In traditional medicine across Asia, various parts of the plant have been used to treat digestive issues, respiratory ailments, and skin conditions.
• The thick, fragrant rind is candied and used as a key ingredient in fruitcakes, panettone, and other rich baked goods.
• The essential oil, extracted by cold-pressing the rind, is a prized component in high-end perfumery and aromatherapy.
• The fruit holds significant religious and ceremonial importance in the Jewish festival of Sukkot, where a specific, unblemished variety known as the 'etrog' is used.
• In traditional medicine across Asia, various parts of the plant have been used to treat digestive issues, respiratory ailments, and skin conditions.
Fun Fact
The citron was the first citrus fruit known to the ancient Romans, who valued it primarily as a perfume and a moth repellent, placing the fragrant fruits among clothes. The fruit's scientific name, Citrus medica, reflects its historical journey through Media (ancient Persia), while its common name 'citron' is the source of the modern word 'citrus' itself. The famous 'Buddha's Hand' citron is a variety where the fruit segments are completely separated into elongated, finger-like sections, and it is often given as an offering in Buddhist temples, symbolising happiness, longevity, and good fortune.
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