Scientific: Citrus x sinensis (Synonyms: Citrus aurantium var. sinensis, Citrus indica, Citrus sinensis)
Common: sweet orange
Family: Rutaceae
Origin: A hybrid between pomelo (Citrus maxima) and mandarin (Citrus reticulata).
Taxonomic confusion: The genus Citrus is frought with many taxonomic issues that are believed to have arisen because cultivars of the main cultivar groups (i.e., oranges, lemons, grapefruits, and limes) are thought to be ancient anthropogenic hybrids, naturally-occurring hybrids, or selections of wild species.
Pronounciation: CI-trus X sigh-NEN-sis
Hardiness zones:
Sunset 12-24
USDA 9-11
Landscape Use: Accent, edible gardens, residential fruit tree, mesic and oasis landscape design themes, attracts bees.
Form & Character: Upright, rounded, symmetrical, domestic, colorful, abundant.
Growth Habit: Evergreen, woody perennial large shrub to small tree, moderate growth rate to 10- to 20-feet tall with similar spread.
Foliage/Texture: Medium green, glaborous and leathery leaves are oblong, elliptical, or oval, tapering to a blunt tip, 3-inches long, 1.5-inches wide, petiole wings are slim to absent, lamina midvein is prominent; medium texture.
Flowers & Fruits: Flowers are borne in small clusters in leaf axils, flower buds are purplish, but open flowers have five distinct white petals, up to 2-inches across, highly fragrant. Flowers are hermaphroditic (has both male and female organs), self fertile, pollinated by bees; fruits are a hesperidium berry, globose to oblong, 3- to 5-inches long, fruit apex occassionally nippled, the green exocarp ripens to orange with smooth to bumpy rinds dotted with oil glands, the fleshy endocarp has 8 to 10 segments (carpels) each sometimes containing seeds.
Seasonal Color: Orange fruits typically ripen in late fall and winter, seasonal color derived from fruits is cultivar specific.
Temperature: Cold hardy to 26oF and heat intolerant above 116oF. Significant heat stress injury (leaf yellowing and necrosis) occurs above 110oF, especially if located in full western sun. Fruit ripening (full orange coloration of fruit exocarp or rind) is enhanced by exposure to winter temperatures below 50oF.
Light: Full sun to filtered shade or some shade from western summer sun, no full shade.
Soil: Tolerant, but well drained soils is essential. Maintaining adequate to optimal soil fertility levels crucial for successful culture of orange. Generally, orange like other citrus will need to be fertilized with a balanced, complete fertilizer containing micronutrient supplements (Fe, Zn, and Mn) three times each year (January, May and September).
Watering: Moderate and consistent patterns of supplemental irrigation are neccesary for successful desert culture, but irrigation frequency and duration varies with time of year and soil texture. In general, flooded, berm irrigations are superior to drip irrigation (less accumulation of soil salts in the rhizosphere).
Pruning: Only infrequent, 'light' corrective pruning is necessary. Citrus prefer to have a full dense, descending canopy of leaves at all times. Pruning strategies should always NOT incude crown raising because all Citrus taxa trunks are HIGHLY prone to sunscald injury if exposed to direct summer sunlight.
Here's a sustainable tip: If the 'Horticultural clods of Phoenix' (aka 'Hort clods') have wandered (like migrant nomads) into your yard and 'lolly popped' your orange trees by raising the crown base to expose their trunks to direct sunlight, then promptly respond by painting the trunk surfaces with a mixture of white flat latex paint and water (1:1 ratio) to protect the exposed trunks from summer sunscald injury.
Propagation: Softwood or semi-hardwood stem cuttings, grafting, budding, seed propagation (mostly for rootstock). Click here for more information.
Disease and Pests: Citrus are prone to numerous, well-documented, mostly soil-derived, biotic and abiotic pressures. Citrus greening is a serious bacterial disease vectored by two psyllid insects.
Additional comments: Sweet oranges are believed to originated in the tropical regions of Asia such as the Malay Archipelago. Orange culture probably first spread to India, southeast China, east coast of Africa, and the eastern Mediterranean region. The Roman conquests, the development of Arab trade routes, and the expansion of Islam contributed significantly to this dispersal. By the 15th century A.D., orange trees were common in the Canary Islands. Today oranges are cultivated in warm arid, Mediterranean coastal Pacific, subtropical and tropical America countries, the tropical Pacific Islands, northern and eastern Mediterranean Eurasian countries, Australia, and South Africa. Sweet orange fruits are rich in vitamin C, dietary fiber, and also provide some potassium and vitamin A.
There are many wonderful sweet orange selections that perform well in the lower Arizona desert landscape gardens. They are broadly categorized into three groups or types:
Navel oranges - grown primarily for fresh consumption, primarily seedless
Common or blond oranges - grown for fresh consumption or juicing
Blood oranges - red pigmentation in the endosperm due to the accumulation of anthocyanins
