Citrus medica

Evergreen shrub growing 4 m tall by 3 m wide at a medium rate. Hardy to UK zone 10, frost tender. Flowers are insect and bee-pollinated; self-fertile. Notable for attracting wildlife. Tolerates light sandy, medium loamy, and heavy clay soils with good drainage. Grows in mildly acidic and neutral soils. Requires full sun and accepts either dry or moist soil.

Description

A small evergreen tree. It grows up to 3-5 m high and spreads to 2 m across. The stem is stout, erect and thorny. The leaves are green and 20 cm x 10 cm. The tree has fat spines. The leaves have teeth along the edge. The leaf stalk does not have wings. The flowers are white, star shaped and with 5 petals. They have a scent. The fruit are large and long, with a rough skin. The fruit grows to 15-25 cm long by 10-15 cm wide. The flesh is white. The fruit does not have a lot of juice. There are several named cultivated varieties.

Edible Uses

The fruits are made into marmalade, used in salads, or incorporated into liqueurs. The thick rind can be sliced and added to salads or candied for use as a flavouring in cakes, puddings, and confectionery; it is a commercial source of candied peel and is traditionally candied after being cleaned by seawater fermentation. Juice from improved cultivars can be extracted to make beverages and desserts. The lemon-shaped fruit measures 10–20cm long and is used in Asian and Mediterranean cuisine, traditional medicines, perfumery, and religious rituals. Citrus fruits are generally harvested from late autumn to early spring, depending on variety and local climate.

Traditional Uses

The thick layer of inner white skin is used as candied peel. It is also added to salads and used in fruit cakes. The juice of some kinds is used for drinks. The fruit are used for marmalade. Caution: The fruit contain coumarin that with sunlight can cause dermatitis in some people.

Medicinal Uses

Fresh shoots, leaves, flowers, fruits, and seeds have all been used in traditional medicinal preparations to treat asthma, arthritis, headache, stomachache, intestinal parasites, and certain psychological disturbances. Root decoctions are reportedly used in China to treat respiratory problems and backache. The fruits are used to treat malaria, coughs, and colds, and the stem is used in febrifuge pills. Contemporary research has shown that various parts of the plant exhibit anti-catarrhal, capillary-protective, anti-hypertensive, diuretic, antibacterial, antifungal, anthelmintic, antimicrobial, analgesic, antioxidant, anticancerous, antidiabetic, estrogenic, antiulcer, cardioprotective, and antihyperglycemic properties. A nanoemulsion of essential oil from Citrus medica var. sarcodactylis has demonstrated antioxidant, antibacterial, and antibiofilm activity. Properties of specific cultivars have been recognised as relevant in treating cancer, diabetes, and Alzheimer's disease.

Distribution

A subtropical plant. It prefers rich, moist soils. The soils need to be well aerated and not waterlogged. They should be in a protected sunny position. They are drought and frost tender. It needs temperatures between 12°C and 35°C. It suits hardiness zones 9-11. In Yunnan.

Where It Grows

Africa, Andamans, Asia, Australia, Bangladesh, Bhutan, Brazil, Cambodia, Cameroon, Cape Verde, Central Africa, Central America, China, Colombia, Congo DR, Cook Islands, Costa Rica, Côte d'Ivoire, Cuba, Dominican Republic, East Africa, Ecuador, Ethiopia, Europe, Fiji, Greece, Guinea, Guinée, Guyana, Haiti, Hawaii, Himalayas, India, Indochina, Indonesia, Iran, Iraq, Israel, Italy, Ivory Coast, Japan, Korea, Laos, Madagascar, Malaysia, Maldives, Mediterranean, Mexico, Middle East, Myanmar, Nepal, Nicaragua, North Africa, North America, Northeastern India, Pacific, Pakistan, Papua New Guinea, PNG, Peru, Philippines, Samoa, SE Asia, Senegal, Serbia, Slovenia, Solomon Islands, South Africa, Southern Africa, South America, Spain, Sri Lanka, Suriname, Taiwan, Tanzania, Thailand, Tibet, Tonga, Turkey, Türkiye, USA, Vanuatu, Vietnam, West Africa, West Indies,

Cultivation

Three main climates are suitable for commercial citrus production - tropical climates, subtropical with winter rain, such as in the Mediterranean and semitropical with summer rainfall, as found in Florida and southern Brazil. Prefers a deep, well-drained but moisture-retentive loamy soil in full sun. Prefers a pH of 6.5 - 7, tolerating 5.5 - 8. Prefers a position sheltered from strong winds. In the tropics, citron grows very well at elevations below 1,300 metres. The optimal temperatures for cultivation range between 15 - 27°c, with the coldest month having an average minimum of at least 15°c. Growth generally ceases below 13°c and above 35°c. Fruits are killed if the temperature falls to -2°c, whilst the leaves are killed at -9°c. Irrigation will be necessary if there are more than three months of dry periods. Citron is very sensitive to frost, intense heat, and drought; it is the tenderest of all Citrus species. The tree has a short life cycle compared with other citrus species. It starts producing when 2 - 3 years old, reaches a maximum in 8 - 15 years and has an economical life of 25 - 30 years. Mature trees produce about 40 kg of fruit per year, but yields of up to 100 kg per year per tree have been obtained. Citron cultivars are divided into two groups:- Acid cultivars. These have pinkish floral buds and shoots, acid pulp, a dark inner seed coat, and a chalazal spot. Non-acid cultivars. These are without pinkish floral buds and shoots, with non-acid pulp, a colourless inner seed coat and a pale-yellow chalazal spot; in China, Japan, Indo-China and India, Citrus medica L. Var. Sarcodactylis (Noot.) Swingle is widely cultivated. It is the fingered citron or Buddha's Hand Citron, whose fruit is split into several finger-like sections without or with very scanty pulp. It is highly esteemed for its fragrance and beauty and is used in perfume rooms and clothing. Grown as a dwarf plant, it is also a valued ornament throughout the Far East. The native range of this species is W. Central Himalaya to Myanmar. It is a shrub or tree and grows primarily in the subtropical biome. It is used as animal food, poison, and medicine and has environmental and social uses for food. Citron is a straggly evergreen shrub or small tree, ranging in height from 3 to 5 m, with fruit borne on thorny branches. Compared to other Citrus species with a life expectancy of 15–18 years, a short-lived plant is very sensitive to frost, intense heat and drought; citron is considered the tenderest of all Citrus species. Citron flowers are borne in clusters of 5–20 blooms throughout the year. The fruit is fragrant and typically oblong but demonstrates considerable phenotypic plasticity, with various shapes and smooth or rough fruits sometimes occurring on the same branch (Morton 1987). The fruit ripens from green to yellow or even orange. Soil Texture: Prefers light (sandy) or medium soils. It can tolerate some heavier soils as long as they are well-drained. Soil Moisture: Requires moist soil but not waterlogged conditions. Irrigation is necessary during dry periods. Drainage: Needs well-drained soil to prevent root rot and fungal issues. Soil pH: Grows best in neutral to slightly acidic soils (pH 6.0–7.5). It can tolerate slightly alkaline conditions but thrives in mildly acidic environments. Saline Tolerance: Moderately sensitive to saline soils and irrigation water with high salt content. Tolerance of Poor Soil: Prefers fertile, well-amended soils. It does not thrive in poor soils unless amended with organic matter. Light Requirements: Requires full sun for optimal growth and fruit production. It can tolerate very light shade but may result in reduced fruit yield. Height: Typically grows to about 2.5–5 meters (8–16 feet) tall, though it can be pruned to a smaller size for cultivation. Pollination: Pollinated by insects, particularly bees. It is self-fertile and does not require cross-pollination. Temperature: Prefers warm climates and is sensitive to frost. Ideal for USDA zones 9–11. Protect from cold winds and frost in cooler regions. Watering: Regular watering is required during dry spells, but overwatering should be avoided. Nutrient Needs: Benefits from regular fertilisation with citrus-specific fertilisers containing nitrogen, phosphorus, potassium, and micronutrients like magnesium and iron. Flowering and Fruiting: Produces fragrant white flowers followed by large, bumpy yellow fruits. Citron fruits are prized for their thick rind, often candied or used for flavouring. Pests and Diseases: Susceptible to common citrus pests such as aphids, scale insects, and citrus leaf miners. Diseases include root rot, citrus canker, and greening disease. Pruning: Regular pruning helps maintain shape, remove deadwood, and encourage air circulation to prevent fungal diseases. It has been introduced into Alabama, Algeria, Andaman Is., Benin, Borneo, Canary Is., China South-Central, China Southeast, Comoros, Cuba, Dominican Republic, Ecuador, Fiji, Florida, Haiti, India, Jamaica, Laos, Leeward Is., Madeira, Mauritania, Mexico Central, Mexico Southeast, Morocco, Nicobar Is., Oman, Peru, Puerto Rico, Society Is., Sri Lanka, Tibet, Trinidad-Tobago, Tunisia, and Vietnam. Citrus trees are generally medium-growing, taking about 3 to 5 years to start producing fruit after planting, depending on the species and growing conditions. They can reach a height of 10 to 30 feet (3 to 9 meters), with some dwarf varieties available for smaller spaces. Most Citrus species are self-fertile, meaning they can produce fruit without needing another plant for cross-pollination, though cross-pollination can improve fruit sets in some varieties. Citrus fruits are generally harvested in late autumn to early spring, depending on the specific variety and local climate. Citrus trees usually flower in the spring. Some species may have a second flowering period in late summer.

Propagation

Sow fresh seed in containers as soon as ripe after thoroughly rinsing. Sow stored seed in containers as soon as possible. Germination usually takes place within 2–3 weeks at 13°C. Seedlings are prone to damping off and must be watered carefully and kept well ventilated. Seed is usually polyembryonic — two or more seedlings arise from each seed, genetically identical to the parent and typically free of any virus present in the parent. Prick out into individual pots when large enough to handle and grow on until at least 10cm tall before planting into permanent positions. Half-ripe wood cuttings can be taken in a frame; this species roots easily from cuttings, and is typically propagated from leafy cuttings taken from 2–4-year-old branches. Layering in October. Most Citrus species are self-fertile and can set fruit without cross-pollination, though cross-pollination can improve fruit set in some varieties.

Other Uses

Citron has been used since Roman times as a perfume and moth repellent. Citron juice is used in an eco-friendly method of synthesising copper nanoparticles. The fruit plays an important role in Jewish ritual during the autumn harvest festival of Sukkot. In East Asia, it is prized for its fragrance and the essential oil was formerly used in perfumery. Ripe fruits are used to air rooms; dried fruits placed with stored clothes act as an insect repellent; and the juice is used to wash linens. In India, branches of the tree are used as walking sticks.

Production

It is slow growing. It is fairly short lived. Trees begin to bear when 3 years old. Trees reach peak production when 15 years old and may live for 25 years. Trees can produce 2,000 fruit in a year.

Other Information

Fruit are sold in markets. It is common in some Mediterranean countries. Trees and fruit are only occasionally seen in Papua New Guinea. It is cultivated.

Notes

There are 20 Citrus species. Several hybrids have been formed.

Nutrition

Synonyms

Also Known As

Bara nibu, Bara nimbu, Begpura, Bibira, Bijaira, Bijoru, Bimiro, Bodu lunboa, Cedrat, Cidra, Cidron, Fragrant citrus, Gargal, Gilam, Hingkom, Jamir, Jara tenga, Jeruk bodong, Kadaranarathai, Kebbat, Kogilacham, Lapnaram, Lima, Limau susu, Lungamu, Madala, Mahalunga, Mahaphala, Maha-ratadehi, Matalanarakam, Mavalung, Nanya sepen, Nareng, asi, Narthangai, Palsak, Pat lebu, Reak sa'reak kraha'm, Rusaka, Rusakam, Satkora, Shauk-thakwa, Sideran, Siderang, So-manong, Sucade, Taw-shauk, Tipolo, Tume han thar, Turanj, Voamandina, Voasary gasy, Voatonlongo, Wichilla limon, Xiang Yuan, Yuzu

References (100)

• AAK, 1980, Bertanam Pohon Buah-buahan. Penerbitan Yayasan Kanisius, Jogyakarta. p 33
• AAK, 1994, Jeruk, Penerbit Kanisius, Jogyakarta. p 201
• Ambasta, S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 129
• Anderson, E. F., 1993, Plants and people of the Golden Triangle. Dioscorides Press. p 206
• Arora, R. K., 2014, Diversity in Underutilized Plant Species - An Asia-Pacific Perspective. Bioversity International. p 62 (Also as Citrus hassaku)

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