华盛顿脐橙是品质优良而无核的有名品种。这个品种可能是由巴西的一株甜橙树的芽变而来,又从巴西引到美国。以后几乎世界每个生产柑桔的国家,包括南非都引种了这个品种。现在,南非的甜橙栽培总面积中,脐橙在北部占26％,在南部占63％。脐橙是一种特殊的果树,其果实发育的早期对于不良气候条件最为敏感。脐橙的花产生无活性的花粉,如果大片单一品种栽植便产生无子果实。这个习性与脐橙大量落果密切 Washington navel orange is a well-known species of non-nuclear quality. This species may have come from the bud of a sweet orange tree in Brazil and from Brazil to the United States. Almost every country in the world producing citrus later, including South Africa, introduced the breed. Now, of South Africa’s total orange cultivated area, navel oranges account for 26% of the North and 63% of the South. Navel orange is a special fruit tree, the early development of its fruit is most sensitive to bad weather conditions. Navel orange flowers produce inactive pollen, if a large variety of monocultures planted to produce fruitless fruit. This habit and a large number of navel oranges close