Citrus aurantium var. medica Wight & Arnott

A straggly shrub or small tree, up to 3 m tall, with light grey bark and relatively soft wood; twigs angular and purplish when young, turning terete, glabrous, with single axillary spines. Leaves elliptic-ovate to ovate-lanceolate, 5-20 cm x 3-9 cm, cuneate or rounded at base, margins serrate, apex bluntly pointed or rounded; petiole short, wingless or nearly so, not clearly articulated with the blade. Flower buds large, pinkish; flowers perfect or stamine, in axillary few-flowered racemes, 3-4 cm in diameter; petals 5, pinkish externally; stamens 30-40(-60); ovary 10-13-locular, style thick. Fruit an ovoid to oblongoid berry, 10-20 cm long, slightly to considerably rough-tuberculate; peel very thick, yellow, fragrant; segments small, filled with pale green pulp-vesicle; juice acid to mildly acid. Seeds numerous, ovoid, about 1 cm x 0.5 cm, acute, monoembryonic. Citron cultivars are divided into two groups: Acid cultivars and Non Acid cultivars. Acid cultivars, with pinkish floral buds and shoots, acid pulp and a dark inner seed-coat and chalazal spot; some well-known cultivars of this group are: 'Diamante' -the leading cultivar in Italy, and 'Etrog' -botanically also distinguished as Citrus medica L. var. ethrog Engler. It is the main cultivar in Israel, where it is used in Jewish Feast of Tabernacles. Non-acid cultivars, without pinkish floral buds and shoots, with non-acid pulp, a colourless inner seed-coat and a pale-yellow chalazal spot; 'Corsican' is a well-known cultivar, leading in Corsica (France) and in California (United States). 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 (Indonesia: jeruk tangan; Malaysia: limau jari; Thailand: som-mu; Vietnam: phÔt thu), whose fruit is split into a number of finger-like sections, without or with very scanty pulp. It is highly esteemed for its fragrance and beauty and used to perfume rooms and clothing. Grown as a dwarf plant it is also a valued ornamental throughout the Far East. Numerous natural hybrids of citron are found in areas where it is indigenous. There are also a number of ill-defined, citron-like fruits of ancient and unknown origin which remain horticultural curiosities.

Citron flowers throughout the year, in the subtropical most abundantly in spring. The tree has a short life cycle compared with other citrus species. It starts producing when 3 years old, reaches a maximum in 15 years and dies in about 25 years. The fruit is dark green when young and takes about 3 months to turn yellow.

The soil should be moist, well-drained, deep and fertile.

In the tropics citron grows very well at elevations below 1300 m. The best citron locations are those without extreme temperatures. Citron is very sensitive to frost and to intense heat and drought; it is the tenderest of all Citrus species.

Citron spread westward to Persia, becoming the first citrus fruit brought under cultivation in the western world, and eastward into China. It has also been taken to most tropical countries, where it is of little importance. Commercial planting of citron is limited to certain islands in the Mediterranean region (belonging to Italy, Greece, France) and in the mountainous coffee regions of Puerto Rico; it is sparingly cultivated elsewhere.

Citron is usually propagated by leafy cuttings taken from 2-4 year-old branches. Citron can be budded onto rough lemon, grape-fruit, sour and sweet orange, but the fruits remain smaller than those produced from cuttings and citron tends to overgrow the rootstock.

Water sprouts should be eliminated. Low hanging branches are pruned to prevent the fruits touching the soil. In Italy branches are staked and spines are trimmed off to avoid damage to the fruit.

Diseases: Branch knot, caused by the fungus Sphaeropsis tumefaciens, is a serious disease in Puerto Rico. Pests: Most citrus pests also attack citron; mites and scales are often troublesome.

Food: The most important use of citron today is as a source of candied peel used in confections and cakes. Essential oils: Citron fruit has been used since Roman times as a perfume and moth repellent, and to flavour foods. Medicine: The fresh shoots, leaves, flowers, fruits and seeds of citron have all entered into a number of traditional medicinal preparations for the treatment of asthma, arthritis, headache, stomachache, intestinal parasites and certain psychological disturbances (insanity, possession by evil spirits). Decoctions of the roots are reportedly used to treat respiratory problems and backache in China.