The navel orange, a citrus with no seeds, originated with a mutation in 1820 in a sweet orange orchard at a Brazilian monastery. The mutation had a smaller, undeveloped second orange adjoined to the first, resembling the human navel. The mutated orange also was sterile, which is why it had no seeds. The only way this seedless orange tree could reproduce was through grafting, and in 1870, two cultivated navel orange trees were planted in Riverside, California, ground zero for today's navel orange market.
Creating New Trees
Navel orange trees are created by grafting a scion, or upper stem part, of a navel orange tree onto the understock, or base, of a regular sweet orange tree. The graft is wrapped in either graft tape or melted graft wax until it grows together.
Navel orange trees are generally shipped to nurseries, for sale to the general public, when they are around 2 feet tall. They need at least 4 hours of direct sunshine a day after they are planted into the ground. They need enough water to keep the soil moist, 1 inch below the surface, and should be fed high-potash fertilizer every 2 weeks.
A navel orange tree, like regular orange trees, generally begins to flower after its second year in the ground. Flowers generally appear in the winter, although in tropical and subtropical areas like Florida and parts of California, there are multiple blooming cycles each year.
Most flowers wind up dropping to the ground; only a small percentage become fruit. Oranges take a long time to mature, with the fruit taking as long as 14 months to grow from a small green nub into a bright orange navel orange.
Tree growth is slow but steady, with orange trees typically gaining 1 to 2 feet in height each year. It takes navel orange trees about 10 to 15 years to mature, at which point they can be up to 20 feet tall. The optimum fruiting period comes when the tree is 20 to 25 years old. Orange trees have been known to live and bear fruit as long as 250 years, although whether a navel tree can attain that age is unknown since the trees have only been popularly cultivated in the United States since the 1870s.