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a genus of biennial or perennial herbaceous plants of the family Liliaceae. The leaves are succulent and may be hollow and tubular or ribbon-like and flat or channeled; they are tightly grouped on the short stem. The inflorescence is a flat or rounded umbel, emerging from a scarious cap or scathe, and is located on a flower stalk or scape. The inflorescence may be composed of flowers or of aerial bulbils or of both at once. The flowers are small, monoecious, and white, violet, pink, yellow, or greenish in color. Cross-pollination is carried out by bees or flies. The fruit is a triquetrous, three-chambered capsule. The seeds are black, with a hard coating. More than 400 species are distributed in the northern hemisphere, of which about 230 species are found in the USSR, with the greatest number of species growing in Middle Asia, the Caucasus, and Eastern and Western Siberia; fewer species are found in the European USSR and the Far East. Six species are cultivated.
The onion A. cepa is the most common species. It is a biennial or may grow up to four years and is native to Middle Asia and Afghanistan. The bulbs are either flat, elongated, or round, depending on the variety. The dry outer scales may be white, yellow, brown, or purple, while the juicy layers are white, pink, or purple. Depending on the variety, the bulbs contain 2.4-14 percent sugar, 2-13.9 milligram (mg) percent vitamin C, and 12-162 mg percent essential oil (which imparts pungency); the leaves contain 25-47.7 mg percent vitamin C and 1.3-5.9 mg percent carotene (provitamin A). The onion A. cepa is used for food in fresh, cooked, fried, preserved, and dried form, as well as for medicinal purposes. The yield may be as high as 400 quintals per hectare (ha) and more. In the USSR about 80 varieties have been produced for specific areas. They are classified according to the number of bulbs produced per cluster as small (one or rarely two per cluster), medium (two or three, occasionally four), and multiple cluster (four to five and more) varieties. They are also classified according to taste (which depends on the quantity of essential oils) as pungent, semipungent, and sweet. The onion A. cepa is unknown in a wild form. It has been cultivated since at least 4000 B.C. Large crops of the onion are grown in the USSR, the United States, Bulgaria, Spain, Egypt, France, Italy, and Japan.
In the Soviet Union the onion A. cepa is grown everywhere. The soil must be fertile, nonacidic, and free from weeds. The basic method of preparing the soil is fall plowing, during which on noncontinuously cultivated soddy podzolic soils of the northern and central European parts of the USSR, 30-45 tons per ha of manure or compost is applied, and on continuously cultivated soils of this type and chernozem soils, 10-15 tons per ha is used. In spring the following amounts of mineral fertilizers are applied (kg/ha): on soddy podzolic soils—N, 50-80; P2O5, 30-50; and K2O, 60-90; on chernozem soils the corresponding figures are 45-60, 45-60, and 60-90. Onions are planted on furrow crowns, ridges, or flat fields. The commercial onion may be grown in one, two, or three years. Large bulbs are obtained in a single year (one-year crops) in southern regions of the USSR by planting seeds directly into the ground or by transplanting seedlings that are 50-60 days old. In two- or three-year crops, large bulbs are obtained in either the second or third year, respectively. In the first year the bulbs grow to be 1.5-2.2 cm in diameter; while in the second year they grow to be more than 3 cm in diameter. The chief pests are the onion fly, Eumenus strigatus, Ceutorrhynchus pleurostigma, onion thrips, stem nematode, and leek moth. The main diseases are onion neck rot, downy mildew, onion smut, and virus diseases.
The Welsh, or spring, onion (A. fistulosum) is a perennial plant that does not form bulbs. It originated in China. There are four subspecies: Russian, Japanese, Chinese (not common in the USSR), and multilevel, which forms three to four tiers of aerial bulbils on the flower stalk. Either the leaves or stem is used for food in fresh or cooked form. The yield is more than 300 quintals per ha. The Welsh onion is grown in the same area for two to four years and more. Multilevel varieties are suitable for forcing in winter in greenhouses.
Leek (A. porrum) is a perennial plant originating in the Mediterranean area. The leaves are long and flat. The height of the plant is 45-80 cm. This species is widely cultivated in Western Europe; in the USSR it is cultivated in the southern European part and Transcaucasia. The leaves and the stem are used for food both in fresh and cooked form. The Karatanskii variety is slightly pungent, while the Bulgarian variety is semipungent in taste. The yield is up to 250 quintals per ha.
The shallot (A. ascalonicum; named after an island in the Aegean Sea) is a perennial plant from southern Asia; some researchers consider it to be a variety of A. cepa. It has been cultivated since antiquity in countries of the Mediterranean area; in the USSR it is grown in southern regions. The young bulbs and the leaves are used for food in both fresh and pickled form. It is suitable for spring planting (forcing) in protected and open fields. The varieties that are grown from seeds are Kushchevka Kharkovskaia, Kubanskii Zheltyi D-322, and Vanskii Mestnyi. The Russkii Fioletovyi and Zaporozhskii varieties, among others, are propagated vegetatively.
Chive (A. schoenoprasum) is a perennial plant from southern Asia. It forms many branches, as many as 100 per plant. The leaves are small and spike-shaped; they contain 70-105 mg percent of vitamin C. The green leaves, which have a delicate flavor, are used for food. Chives are suitable for forcing in winter in greenhouses and may be grown in the same field for four or five years. At times they are cultivated as ornamentals and as nectariferous plants.
Garlic (A. sativum) is a vegetatively propagated species of Allium and a valuable vegetable.
Certain wild species of Allium are also used for food, such as A. nutans, rocambole (A. scorodoprasum), ramson (A. ursinum), and A altaicum. Members of this genus raised as ornamentals include A. pskemense, which reaches a height of 1 m, A. coeruleum, which has bright blue flowers, and A. altissimum, which reaches a height of 1.5 m and has violet flowers. The presence of plants of the genus Allium among grasses in pastures and meadowland is undesirable, since when found mixed with feed eaten by animals, they impart an unpleasant taste to milk. Potherb onion (A. oleraseum) and A. rotundum are weeds in fields of rye.
REFERENCESAlekseeva, M. V. Ku’turnye luki. Moscow, 1960.
Biokhimiia ovoshchnykh kul’tur. Moscow-Leningrad, 1961.
Kazakova, A. A. Luk. Leningrad, 1970.
Erenburg, P. M., and A. S. Laosin. Luk i chesnok Alma-Ata, 1971.
I. I. ERSHOV