Does grafting a sour orange seedling make it sweet?
A: No. The sour orange is Citrus aurantium. It is also known as the Seville orange, famed for its use in English marmalade. Sweet orange is Citrus sinensis, an entirely different species. Sour oranges will always be sour, and sweet oranges will always be sweet. In areas of the world where tristeza virus is not present, sweet orange grafted to sour orange rootstock gives sweet oranges of exceptionally good quality. But the tristeza virus has made that combination rarer and rarer, recently, since it kills the trees. Sour orange can be grown as a scion, but its fruits will always be sour, regardless of the rootstock used.
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