The bitter or Seville Orange is seldom cultivated in Pakistan. Mostly used as a rootstock in grafting other citrus species; the fruit may be used for marmalades.

Oranges and grapefruit are Citrus maxima × C. reticulata and the backcrosses with the parental species. Many of these hybrids arose in China, although others were synthesized, especially in the U.S.A., and introduced in China. The cultivars can be arranged in groups: Sour Orange Group (the sour or bitter orange most like the original cross), Sweet Orange Group (the commercially most important being backcrosses with C. reticulata ), and Grapefruit Group (representing backcrosses with C. maxima and first being made in the Caribbean).

Sweet Orange Group
Petiole long and narrow; leaf blade ovate, ovate-elliptic, or rarely lanceolate, 6-10 × 3-5 cm or larger. Calyx lobes 3-5. Petals white or rarely purplish, 1.2-1.5 cm. Style stout; stigma large. Fruit orangish yellow to orangish red, globose, depressed globose, or ellipsoid; sarcocarp with 9-12 segments, yellow, orange, or purplish, sweet or slightly acidic. Seeds few or absent; seed coat slightly ridged; embryos numerous; cotyledons milky white. Fl. Mar-Jun, fr. Oct-Dec but some cultivars Feb-Apr. 2n = 18, 27, 36, 45.

Below 1500 m. Cultivated S of the Qin Ling, as far NW as SE Gansu and as far SW as SE Xizang.

Grapefruit Group
Branches glabrous. Leaves similar to those of Citrus maxima but leaf blade smaller and narrower, midvein ciliate. Flowers smaller than those of C. maxima. Calyx lobes glabrous. Fruit yellow, depressed globose to globose, smaller than those of C. maxima; pericarp thin; sarcocarp with 12-15 segments, yellowish white or pink, tender, juicy, slightly fragrant and acidic. Seeds few or absent; embryos numerous. Fr. Oct-Nov. 2n = 18, 20, 27, 36.

Tree, 7-8 m tall, spines axillary and sharp. Leaves 50-115 x 30-55 mm, elliptic; petiole winged, wings obovate. Flowers bisexual, 1-few, in axillary cymes. Petals fleshy and glandular. Stamens 20-24. Fruit globose, 7 x 7.5 cm, flattened at the base and apex; rind when ripe, glandular and rough. Axis hollow. Pulp bitter-acidic.

Small trees. Branches with spines up to ca. 8 cm. Petiole obovate, 1-3 × 0.6-1.5 cm, base narrow; leaf blades dark green, thick. Inflorescences racemes, with few flowers or flowers solitary. Flowers perfect or male by ± complete abortion of pistil; buds ellipsoid to subglobose. Calyx lobes 4 or 5. Petals 2-3.5 mm in diam. Stamens 20-25, usually basally connate into bundles. Fruit orange to reddish, globose to oblate, surface coarse; pericarp thick, sometimes difficult to remove; sarcocarp with 10-13 segments, acidic and sweet or sometimes bitter. Seeds numerous, large, with ridges; embryo(s) solitary to numerous; cotyledons milky white. Fl. Apr-May, fr. Sep-Dec. 2n = 18.

Himalaya (Garhwal to Sikkim), Khasia, Assam, China, Indo-China, Burma. Cultivated.

1000 m

Fl. Per.: March-April. Fr. Per.: Oct.-Nov.

Cultivated and sometimes naturalized in most of China S of the Qin Ling.

Aurantium ×acre Miller; A. ×corniculatum Miller; A. ×distortum Miller; A. ×humile Miller; A. ×myrtifolium Descourtilz; A. ×sinense Miller; A. ×vulgare (Risso) M. Gómez; Citrus ×amara Link; C. ×aurantium subsp. amara Engler; C. ×aurantium var. bigaradia (Loiseleur) Brandis; C. ×aurantium var. crassa Risso; C. ×aurantium var. daidai Makino; C. ×aurantium var. dulcis Hayne; C. ×aurantium var. fetifera Risso; C. ×aurantium var. lusitanica Risso; C. ×aurantium var. myrtifolia Ker Gawler; C. ×aurantium subf. nobilis (Loureiro) Hiroe; C. ×aurantium var. sanguinea Engler; C. ×aurantium subf. sinensis (Linnaeus) Hiroe; C. ×aurantium subsp. sinensis (Linnaeus) Engler; C. ×aurantium var. sinensis Linnaeus; C. ×aurantium subsp. suntara Engler; C. ×aurantium var. vulgaris (Risso) Risso & Poiteau; C. ×aurata Risso; C. ×bigaradia Loiseleur; C. ×changshan-huyou Y. B. Chang; C. ×communis Poiteau & Turpin; C. decumana (Linnaeus) Linnaeus var. paradisi (Macfadyen) H. H. A. Nicholls; C. ×dulcis Persoon; C. ×florida Salisbury; C. ×humilis (Miller) Poiret; C. maxima (Burman) Merrill var. uvacarpa Merrill; C. ×myrtifolia (Ker Gawler) Rafinesque; C. ×paradisi Macfadyen; C. ×sinensis (Linnaeus) Osbeck; C. ×sinensis var. brassiliensis Tanaka; C. ×sinensis subsp. crassa (Risso) Rivera et al.; C. ×sinensis subsp. fetifera (Risso) Rivera et al.; C. ×sinensis subsp. lusitanica (Risso) Rivera et al.; C. ×sinensis var. sanguinea (En gler) Engler; C. ×sinensis var. sekkan Hayata; C. ×sinensis subsp. suntara (Engler) Engler; C. ×taiwanica Tanaka & Shimada; C. ×tangelo Ingram & H. E. Moore; C. ×vulgaris Risso.

Citrus aurantium, the sour orange (also known as bitter or Seville orange) is a thorny tree up to 10 m tall in the Rutaceae (citrus family) that originated in southeastern China and Myanmar, and is now commercially cultivated primarily in Spain, southern France, China, and Japan for its use in marmalade and candied peels and as an ornamental. The closely related bergamot, which is variously classified as a subspecies (C. aurantium subsp. bergamia) or a separate species (C. bergamia), is thornless and not as tall (to 5 m). Citrus species hybridize readily, and classifications of them vary considerably; in some classifications, this species is considered C. X aurantium, a hybrid between C. maxima and C. reticulata. The original species is now considered critically endangered in its native range, where it is found only in isolated populations in the regions of Hsinchu and Taitung, in China. The sour orange tree has alternate, evergreen, minutely toothed oval to oblong leaves up to 13.75 cm (5 in) long, with broadly winged petioles (leaf stems). Leaves are aromatic and covered with small oil glands. Flowers, which are about 3.75 cm wide (1.5 in) are fragrant, with 5 slender white petals and 24 yellow stamens, and may occur singly or in small clusters. The fruit is round to somewhat flattened, up to 8 cm (3.12 in) wide, and ripens to orange or reddish orange. The fruit rind or peel is thick and aromatic, with a rough surface dimpled with tiny oil glands. The flesh or pulp is separated into 10 to 12 segments, with few to many hard seeds, and is often hollow in the middle. In addition to being cultivated for its fruit, sour orange is also used as a hardy rootstock for many other citrus varieties. Sour oranges are sour from high acidity, as well as bitter, are not considered edible fresh; they are primarily processed into marmalade. The juice may be used as a flavoring or similar to vinegar in some regional cuisines. “Bitter orange oil,” extracted from the peels, is used to flavor candy, chewing gum, baked goods, soft drinks, and liqueurs, including Curaçao, Cointreau, and Grand Marnier, as well as in the bitter orange French “sauce bigarande” to accompany roast duck. The popular Italian beverage, chinotto, comes from the sour orange variety, Citrus uranium var. myrtifolia. Bergamot, which is likely of hybrid origin, is prized primarily for its highly aromatic oil, which was an ingredient in eau de cologne, the perfume originally developed in Cologne, Germany during the 17th century. It is also used to flavor Earl Grey tea. Bergamot is produced mostly in the Calabrian region of Italy. (Bailey et al. 1976, Morton 1987, van Wyk 2005, Wikipedia 2012.)

Citrus paradisi, grapefruit, is a medium-sized fruit tree in the Rutaceae (citrus family) of recent hybrid origin. It is thought to have originated in the Caribbean as a cross between a pomelo (C. maxima) and a sweet orange (C. sinensis); it was first described in Barbados in the 1750s and popularized in the Caribbean and the U.S. Diverse cultivars of this fruit tree are now cultivated in many tropical, semi-tropical, and warm temperate regions world-wide for the sweet-sour fruit that is often served as a breakfast food.

The grapefruit tree typically grows 4.5 to 6 m (15 to 20 ft) tall, although old trees may grow to heights of 13 m or more, with spiny twigs. The leathery, evergreen leaves are typically ovate, 7.5 to 17.5 cm (3 to 7 in) long, and 4.5 to 7.5 cm wide.The aromatic white flowers usually grow in clusters of 2 to 20 and produce large globose to pear-shaped fruits that ripen to light yellow or yellow orange and are 10 to 15 cm in diameter. Fruits have thick skins pitted with oil glands. Diverse cultivars have been developed, with fruit flesh, which is typically quite juicy, dividing into 11 to 14 segments and varying from yellow to orange to pinkish red, with few to many seeds. Flavor ranges from sweet-tart to sour or bitter. The fruits can be left on the tree for several months to lengthen the harvest season and they keep well in storage.

Grapefruits, which are high in potassium and vitamins A and B but lower in vitamin C than many other citrus fruits, are often served as a fresh fruit—frequently as a breakfast food in the U.S., or sprinkled with sugar and grilled as a dessert. The fruit may be processed into juice for use in beverages, cocktails, fruit salads, sorbets, and desserts, and sometimes used in cooking. The whole fruit can be used to make marmalades.

Grapefruits became famous as a diet food starting in the 1930s, in a diet program again made famous in the 1970s, but claims of their fat-combating properties have not been substantiated. Grapefruits and pomelos do, however, contain a class of compounds, known as furanocoumarin derivatives, that interfere with the action of various prescription medications.

Total 2010 global production of grapefruits (together with pomelos) harvested commercially was 7.0 million metric tons from 269,002 cultivated hectares. China and the U.S. were the leading producers, together producing nearly 60% of the world total. Other major producers include Mexico, South Africa, and Thailand. Grapefruit trees and fruits are susceptible to various pests and pathogens, including the Mediterranean fruit fly (Ceratitis capitata), numerous fungal leaf spots, blights, and root rots (Cercospora, Colletotrichum, Fusarium, Phytophthora, and others) and viruses that can significantly reduce yields.

(Bailey et al. 1976, FAOSTAT 2012, Morton 1987, van Wyk 2005, Zelman 2012, Zeratsky 2012.)

Papilio demodocus demodocus (Citrus swallowtail) Papilio ophidicephalus chirinda (Emperor swallowtail) Papilio dardanus cenea (Mocker swallowtail)

Citrus vulgaris Risso, Ann. Mus. Paris 20: 190. 1813
Citrus bigaradia Loisel. Nouv. Duham. 7 : 99. 1819.
Citrus Aurantium vulgaris Wight & Arn. Prodr. 1 : 97. 1834.
Citrus Aurantium bigaradia Hook. Fl. Brit. Ind. 1 : 515. 1872.
A small tree 6-9 m. in height, the young twigs light-green, armed with sharp, alternate thorns ; leaves unifoliolate, evergreen, alternate; leaflet ovate, 6-12 cm. long, 3.5-10 cm. broad, often acuminate ; petioles commonly broadly winged ; flowers in small axillary cymes, sweet-scented, somewhat larger than those of the preceding ; sepals often bluntish ; petals oblong, white ; berry dark-orange, or frequently reddish when mature, the rind thick, more or less roughened, strongly aromatic, bitter, the pulp sour and bitter.
Type locality: (Cultivated.)
Distribution : Cultivated ; thoroughly naturalized in tropical and subtropical regions.

Citrus aurantium L,. Sp. PI. 782. 1753 A tree 6-12 m. in height, with light-green, glabrous twigs angled toward their ends, the branches smooth, grayish-brown, often armed with small, sharp thorns ; petioles commonly narrowly winged, or wingless; leaves uuifoliolate, evergreen; leaflet oblongovate to ovate or oval, 6.5-13 cm. long, 3-10 cm. broad, acute or sometimes rounded at the apex, cuneate to rounded at the base, dark -green and shining above, paler beneath, entire or crenulate; flowers very fragrant, in axillary clusters of 1-6; sepals more or less sharppointed ; petals oblong, 11-18 mm. long, pure white, thick and fleshy ; berry globose or subglobose, 6-9 cm. long, 6.5-9.5 cm. broad, the rind usually thin, smooth or wrinkled, the pulp abundant, sweet or sour.
Type locality : India.
Distribution : Widely cultivated ; naturalized in tropical and subtropical regions.

Citrus myrtifolia, the myrtle-leaved orange tree, is a species of Citrus with foliage similar to that of the common myrtle. It is a compact tree with small leaves and no thorns which grows to a height of three metres (10 ft) and can be found in Malta, Libya, the south of France, and Italy (primarily in Liguria, typically Savona, and also in Tuscany, Sicily, and Calabria).

The fruit of the tree resemble small oranges. It has a bitter flavor and is commonly called by its Italian name, chinotto (Italian pronunciation: [kiˈnɔtto]). It is an essential flavoring agent of most Italian amari, of the popular Campari apéritif, and of several brands of carbonated soft drinks that are generically called "chinotto".

Citrus myrtifolia is sometimes planted in gardens. Due to its compactness, it can also be planted in a pot or other container.

Chinotto at the Botanical Garden of the Brissago Islands