The citron is borne by a slow-growing shrub or small tree reaching 8 to 15 ft (2.4-4.5 m) high with stiff branches and stiff twigs and short or long spines in the leaf axils. The leaflets are evergreen, lemon-scented, ovate-lanceolate or ovate elliptic, 2 1/2 to 7 in (6.25-18 cm) long; leathery, with short, wingless or nearly wingless petioles; the flower buds are large and white or purplish; the fragrant flowers about 1 1/2 in (4 cm) wide, in short clusters, are mostly perfect but some male because of pistil abortion; 4- to 5-petalled, often pinkish or purplish on the outside, with 30 to 60 stamens. The fruit is fragrant, mostly oblong, obovoid or oval, occasionally pyriform, but highly variable; various shapes and smooth or rough fruits sometimes occurring on the same branch; one form is deeply divided from the apex into slender sections; frequently there is a protruding style; size also varies greatly from 3 1/2 to 9 in or even 1 ft (9-22.8 or 30 cm) long; peel is yellow when fully ripe; usually rough and bumpy but sometimes smooth; mostly very thick, fleshy, tightly clinging; pulp pale-yellow or greenish divided into as many as 14 or 15 segments, firm, not very juicy, acid or sweet; contains numerous monoembryonic seeds, ovoid, smooth, white within.
Origin and Distribution
Citron cultivars are mainly of two types: 1) those with pinkish new growth, purple flower buds and purple-tinted petals, acid pulp and dark inner seed coat and chalazal spot; 2) those with no pink or purple tint in the new growth nor the flowers, with non-acid pulp, colorless inner seed coat, and pale-yellow chalazal spot. Among the better-known cultivars are:
'Corsican'–origin unknown but the leading citron of Corsica; introduced into the United States around 1891 and apparently the cultivar grown in California; ellipsoid or faintly obovate, furrowed at base; large; peel yellow, rough, lumpy, very thick, fleshy; pulp crisp, non-juicy, non-acid, seedy. Tree small, spreading, moderately thorny with some large spines.
'Diamante' ('Cedro Liscio'; possibly the same as 'Italian' and 'Sicilian')–of unknown origin but the leading cultivar in Italy and preferred by processor's elsewhere; long-oval or ellipsoid, furrowed at base, broadly nippled at apex; peel yellow, smooth or faintly ribbed; very thick, fleshy; pulp crisp, non-juicy, acid; seedy. Tree small, spreading, thorny as 'Corsican'. Very similar is a cultivar called "Earle" in Cuba.
'Etrog' ('Ethrog', 'Atrog'; C. medica var. Ethrog Engl.)–the leading cultivar in Israel; ellipsoid, spindle-shaped or lemon-like with moderate neck and often with persistent style at base; usually with prominent nipple at apex; medium-small as harvested; if not picked early, it will remain on the tree, continuing to enlarge for years until the branch cannot support it. For ritual use, the fruit should be about 5 oz (142 g) and not oblong in form. Peel is yellow, semi-rough and bumpy, faintly ribbed, thick, fleshy; flesh is crisp, firm, with little juice; acid; seedy. Tree is small, not vigorous; leaves rounded at apex and cupped. This cultivar has been the official citron for use in the Feast of the Tabernacles ritual but if unavailable any yellow, unblemished, lemon-sized citron with adhering style can be substituted.
'Fingered Citron', Plate XXI, ('Buddha's Hand', or 'Buddha's Fingers'; C. medica var. sarcodactylus Swing.); called fu shou in China, bushukon in Japan, limau jari, jeruk tangan, limau kerat lingtang, in Malaya; djerook tangan in Indonesia; som-mu in Thailand; phât thu in Vietnam. The fruit is corrugated, wholly or partly split into about 5 finger-like segments, with little or no flesh; seedless or with loose seeds. The fruit is highly fragrant and is placed as an offering on temple altars. It is commonly grown in China and Japan; is candied in China.
In India, there are several named types, in addition to the 'Fingered', in the northwest:
'Bajoura'–small, with thin peel, much acid juice.
'Chhangura'–believed to be the wild form and commonly found in a natural state; fruit rough, small, without pulp.
'Madhankri' or 'Madhkunkur'–fruit large with sweetish pulp.
'Turunj'–fruit large, with thick peel, the white inner part sweet and edible; pulp scant, dry, acid. Leaves are oblong and distinctly notched at the apex.
Climate
Soil
Propagation
Culture
In 'Etrog' orchards, the Israeli growers are careful to take every precaution to protect the fruit, tying the fruiting branch securely in place and trimming away any twigs that might touch the fruit. To avoid moving irrigation equipment through the groves, the trees are manually watered and frequently sprayed to eliminate destructive insects.
If citrons are allowed to fully ripen on the tree they will be very aromatic and the peel yellow, the inner peel very tender. In India, a fruiting branch may be bent down and the immature fruit put into a jar shaped like a human head (or other form) so that the mature fruit will be of the same shape. These are sold as curiosities and are said to be intensely fragrant.
Harvesting
Pests and Diseases
Horticulturists in Florida report that citron trees in this state are nearly always unthrifty, are subject to gummosis, and usually in a state of decline and dieback, and are accordingly poor bearers.
Branch knot, caused by the fungus Sphaeropsis tumefaciens, was first noticed on citron trees in Puerto Rico in 1977. By 1983, it had become a serious threat to the local citron industry. The deformations become large and necrotic, lead to witches' broom, dieback and breaking of branches.
Food Uses
Puerto Rican food technologists reported in 1970 that the desalted citron could be dehydrated in a hot air tray dryer at 108º F (42.22º C), reducing the weight by 95% to lower costs of shipment, then stored in polyethylene bags and later reconstituted and candied. In 1979, after further experiments, it was announced that fresh citron cubes, blanched for 1/2 minute in water at 170º F (76.7º C) can be candied and the product is equal in quality to the brined and candied peel, and this procedure saves the costs of salt, storage, and shipping of heavy barrels. If the citron lacks flavor, a few orange or lemon leaves may be added to the sirup.
The fruit of the wild 'Chhangura' is pickled in India. In Indonesia, citron peel is eaten raw with rice. The entire fruit of the 'Fingered citron' is eaten.
If there is sufficient juice in the better cultivars, it is utilized for beverages and to make desserts. In Guatemala, it is used as flavoring for carbonated soft-drinks. In Malaya, citron juice is used as a substitute for the juice of imported, expensive lemons. A product called "citron water" is made in Barbados and shipped to France for flavoring wine and vermouth.
In order to expand the market for citron, Puerto Rican workers have established that the green-mature fruits can be peeled by immersing in a boiling lye solution to save the labor of hand-peeling and then the fruits can be made into marmalade, jelly, and fruit bars that are crusty on the outside, soft within.
In Spain, a sirup made from the peel is used to flavor unpalatable medical preparations.
Food Value Per 100 g of Edible Portion*
Fruit: Chinese and Japanese people prize the citron for its fragrance and it is a common practice in central and northern China to carry a ripe fruit in the hand or place the fruit in a dish on a table to perfume the air of a room. The dried fruits are put with stored clothing to repel moths. In southern China, the juice is used to wash fine linen. Formerly, the essential oil was distilled from the peel for use in perfumery.
Leaves and twigs: In some of the South Pacific islands, "Cedrat Petitgrain Oil" is distilled from the leaves and twigs of citron trees for the French perfume industry.
Flowers: The flowers have been distilled for essential oil which has limited use in scent manufacturing.
Wood: Branches of the citron tree are used as walking-sticks in India. The wood is white, rather hard and heavy, and of fine grain. In India, it is used for agricultural implements.
Medicinal Uses: In ancient times and in the Middle Ages, the 'Etrog' was employed as a remedy for seasickness, pulmonary troubles, intestinal ailments and other disorders. Citron juice with wine was considered an effective purgative to rid the system of poison. In India, the peel is a remedy for dysentery and is eaten to overcome halitosis. The distilled juice is given as a sedative. The candied peel is sold in China as a stomachic, stimulant, expectorant and tonic. In West Tropical Africa, the citron is used only as a medicine, particularly against rheumatism. The flowers are used medicinally by the Chinese. In Malaya, a decoction of the fruit is taken to drive off evil spirits. A decoction of the shoots of wild plants is administered to improve appetite, relieve stomachache and expel intestinal worms. The leaf juice, combined with that of Polygonum and Indigofera is taken after childbirth. A leaf infusion is given as an antispasmodic. In Southeast Asia, citron seeds are given as a vennifuge. In Panama, they are ground up and combined with other ingredients and given as an antidote for poison. The essential oil of the peel is regarded as an antibiotic.
