Scientific: Citrus aurantium
Common: sour orange
Family: Rutaceae
Origin: southeastern Asia
Pronounciation: CI-trus a-u-RAN-tee-um
Hardiness zones
Sunset 8, 9, 12-24
USDA 9-11
Landscape Use: Sour orange is a small, rounded amenity (colorful sour fruit!) tree for mesic and oasis landscape designs themes.
Form & Character: Everything's rounded (crown to fruit), clean, green, formal, and demanding.
Growth Habit: Evergreen, woody, broadleaf perennial tree, moderate growth rate to 20-feet tall with equal spread.
Foliage/Texture: Leaves are glabrous, dark green, elliptic to ovate with winged petioles, 3- to 4-inches long; medium coarse texture.
Flowers & Fruits: Flowers are fragrant, cream white on axillary meristems; fruits are rounded and orange when ripe.
Seasonal Color: Subtle floral accent in late February to early March. Strong orange-colored fruiting accent from October to May depending on the cultivar.
Temperature: Heat tolerant in Phoenix provided the tree is not situated in a direct western exposure. Cold tolerant to 27oF.
Light: Full sun to partial shade though western Phoenix sun will scald the trunk unless shaded or painted with white latex paint to protect against direct insolation.
Soil: Tolerant, but will show micronutrient deficiency symptoms when grown in soils with high pH.
Watering: Frequent, regular water is a must during the summer months.
Pruning: Seasonal heading back to promote a rounded canopy. Be extremely careful about crown raising citrus as they are HIGHLY prone to trunk sunscald injury caused by direct exposure to insolation.
Propagation: Seed, grafting, budding, stem cuttings. Sour orange has traditionally been used by commercial citrus growers as a rootstock for other eatable citrus varieties; however, recent concerns about the spread of the tristeza virus has caused it to be stopped being used as such.
Disease and pests: Many diseases and pests inflect citrus, most notably is quick decline, or Tristeza disease which afflicts sour orange.
Additional comments: In central Arizona, all citrus require regular applications of supplemental fertilizers consisting of nitrogen (three times a year in February, May and September) and chelated micronutrients (once every other year). Though the fruit endosperm of sour orange is quite sour, it is often used to make marmalades, sauces, liqueurs, drinks, and candies.
Sour orange cultivars include:
Historical tidbit: Many of the older, mature sour orange trees on the ASU Tempe campus were transplanted there during the later 1980's from land that is now part of the ASU Research Park, but was once the ASU Horticultural Research Farm that was an integral part of the now defunct ASU research and teaching horticulture programs.
