647 Citrus sinensisCommon Names: sweet orange, navel orange Family: Rutaceae (citrus Family)
The sweet orange is a compact evergreen tree 20-30 ft (6.1-9.1 m) tall with a rounded, symmetrical crown spreading 15-20 ft (4.6-6.1 m) or so. The leaves are shiny and leathery, oblong to elliptic, up to 4 in (10.2 cm) long, and have narrow wings on their petioles (leaf stems). The twigs on many orange cultivars are thorny. Orange blossoms are white, very fragrant, and arranged in clusters of 1-6. They bloom in spring and give rise to oranges the following autumn or winter. Last year's oranges often are still on the trees when the new flowers are blooming.
Among the many cultivars of oranges are 'Hamlin', a heavy producer of very juicy smooth-skinned fruits with few seeds that are harvested October through January; 'Valencia' is a thin-skinned juice orange grown commercially in California and Florida that produces March through July; 'Washington', the original "navel" orange, is grown mainly in California for the fresh fruit market and is harvested October through January; 'Pineapple' is the leading midseason commercial orange in Florida, fruiting December through February; and 'Parson Brown' which is a midseason juicy and seedy orange for dooryard planting that fruits October through December.
The "blood" oranges are a group of cultivars with especially red flesh and hints of raspberry flavor. They require cool nights to develop the red color. 'Moro', Sanguinelli' and 'Tarocco' are examples. The 'Temple' orange is a hybrid between the sweet orange and the mandarin (C. reticulata).
The sweet orange is native originally to Vietnam, NW India and southern China. It is cultivated in subtropical and tropical areas throughout the world, especially in Brazil and the United States, which together account for over two-thirds of world production. In the continental US, commercial citrus production is mainly confined to zone 9B in Florida, California, the Rio Grande valley in Texas, southern Arizona and extreme southern Louisiana.
CultureLight: Full sun for maximum production, but oranges do quite well in partial shade, or under the light, filtered shade of large pines or oaks. Moisture: Orange trees are fairly drought tolerant, but fruit quantity and size may suffer if supplemental water is not given during prolonged dry periods. Annual rainfall totals of 40-45 in (102-114 cm) are adequate for orange trees. Orange trees cannot tolerate saturated soils. Hardiness: USDA Zones 9 - 11. In zone 9A, orange trees will need occasional protection when temperatures fall below about 24ºF (-4.4ºC). Plant cold sensitive oranges in the warmest part of your landscape, which usually is the south side of a building. Cold hardiness depends on preconditioning. A sudden cold snap will be more harmful than one that comes behind several days of cooling weather. To protect citrus trees from brief cold spells, cover with a blanket and burn a light bulb inside the "tent", or place large containers of water all around the tree. Frost can destroy orange blossoms even if temperatures remain above freezing. To prevent frost from forming, keep the air moving over the blossoms with a fan, or cover with a blanket. Some gardeners place a frame of PVC pipe or 2x4 lumber around their citrus trees in winter and cover with clear plastic sheeting when freezing temperatures threaten. Propagation: Bud cuttings of orange cultivars are grafted onto one or two-year old seedlings of the same or a related species. In bud-grafting, a small patch of bark containing a bud is removed from the scion (donor plant) and inserted beneath the bark of the receiving plant (rootstock). The principal root stocks in use are sour orange (C. aurantium), for areas with good quality soils; 'Rough' lemon or 'Volkamer' lemon (C. limon), used for warm areas with sandy soils; and trifoliate orange (Poncirus trifoliata), used in colder areas.
Gardeners in zones 9-11 know that orange trees make beautiful and carefree specimen trees. With glossy evergreen foliage, highly fragrant blossoms, and ornamental as well as edible fruits, the oranges are hard to beat in the subtropical landscape. Grafted orange trees begin bearing in 2-3 years, and the fruit keeps well on the tree for several months.
The orange blossom is the Florida state flower. Honeybees love orange blossoms and the honey they make is mild and delicious.
The caterpillar of the giant swallowtail butterfly, one of North America's largest and most spectacular butterflies, relies solely on plants in the citrus family for food. The caterpillar, called an "orange dog", is itself a spectacular creature - it looks like a 2 in (5.1 cm) long white and brown mottled bird dropping until disturbed, at which time it extends a bizarre pair of bright orange antler-like "scent horns" (osmateria) that stink to high heaven.
Oranges do not continue ripening after picking, so leave them on the tree until you're ready to use them. Cooler temperatures bring on the orange color, and oranges grown in the tropics remain green until gassed with ethylene. Freshly picked oranges are tastier than those bought in the market which usually have been "de-greened" with ethylene gas, washed with detergent, colored with orange dye, coated with wax, and stored for who-knows-how-long under refrigeration.
Oranges are said to lower cholesterol and aid in the digestion of fatty foods. Unfortunately, the vitamin C in oranges is concentrated mainly in the peel and the white layer just under the peel. There are better sources of vitamin C.
There are about 16 species in the genus, Citrus. See Floridata's Mandarin orange (C. reticulata) profile for a breakdown of the various species of edible citrus.
Steve Christman 4/4/00; updated 11/23/03