The final citrus to think of growing is the commercially grown sweet navel orange, but this needs all-year-round warmth, so will grow well only in a heated greenhouse.
Because the mutation left the fruit seedless and, therefore, sterile, the only method to cultivate navel oranges was to graft cuttings onto other varieties of citrus trees.
Some cultivars of citrus fruits (especially navel oranges), satsumas, mandarin oranges, table grapes, grapefruit, and watermelons are valued for their seedlessness.
