Here's some history from the Citrus Website:
Parentage/origins: Washington navel orange is also known as the Bahia for the Brazilian city from which it was imported into the United States in 1870. Although its origins are uncertain, it is believed to come from a bud sport found in a Selecta orange tree in the early 1800s. Upon its arrival at the U.S. Department of Agriculture in Washington, D.C. it was propagated and trees were sent to California and Florida. Although the Florida trees did not flourish, those sent to Eliza Tibbets in Riverside, California found an ideal climate for their culture. These exceptionally delicious, seedless, easy-peeling fruits quickly attracted the attention of citrus growers, and within a decade the "Washington" navel orange, as it came to be known, was the most widely planted variety in the area.
Season of ripeness at Riverside: November to January
Notes and observations:
EMN, 1985: Buds taken from Parent Washington navel tree growing in plot on Magnolia Avenue, Riverside, Calif. This accession had mild exocortis, removed by shoot tip grafting.
Navel orange trees, in general, and Washington navel orange trees in particular, are not very vigorous trees. They have a round, somewhat drooping canopy and grow to a moderate size at maturity. The flowers lack viable pollen so the Washington navel orange will not pollinate other citrus trees. Because of the lack of functional pollen and viable ovules, the Washington navel orange produces seedless fruits. These large round fruits have a slightly pebbled orange rind that is easily peeled, and the navel, really a small secondary fruit, sometimes protrudes from the apex of the fruit. The Washington navel orange is at its best in the late fall to winter months, but will hold on the tree for several months beyond maturity and stores well.
