Walnuts are the oldest tree food known to man, dating back to 7000 B.C. The Romans called walnuts Juglans regia, “Jupiter’s royal acorn.” Early history indicates that English walnuts came from ancient Persia, where they were reserved for royalty. Thus, the walnut is often known as the “Persian Walnut.” Walnuts were traded along the Silk Road route between Asia and the Middle East. Caravans carried walnuts to far off lands and eventually through sea trade, spreading the popularity of the walnut around the world. English merchant marines transported the product for trade to ports around the world and they became known as “English Walnuts.” England, in fact, never grew walnuts commercially. The outer shell provided a natural protective layer helping to maintain the quality of the nut. Today the nut trade continues to be a well-established, ordered, and structured business, and the California walnut is well known as the top quality walnut for the world.
Learn more about the history of walnuts: Historical Virtues of Walnuts
The walnut was first cultivated in California by the Franciscan Fathers in the late 1700s. The earliest walnuts to enter California were known as “mission” walnuts. Unlike today’s walnuts, these first entries were small with hard shells. The trees flourished in the Mediterranean-like climate zones of California, and by the 1870s modern walnut production had begun with orchard plantings in southern California, near Santa Barbara. In the next 70 years the center of California’s walnut production shifted with successful plantings in the central and northern parts of the state. Many of today’s improved cultivars are descendants of early plantings.
Luther Burbank is credited with early research in California walnut cultivation. Read more about him, here: Luther Burbank
The first commercial plantings began in 1867 when Joseph Sexton, an orchardist and nurseryman in the Santa Barbara County town of Goleta, planted English walnuts. For several years, walnuts were predominantly planted in the southern areas of California, accounting for 65% of all bearing acreage. Some 70 years after Sexton’s first planting, the center of California walnut production moved northward to the Central Valley area in one of the most dramatic horticultural moves in history. Better growing areas, improved irrigation, and better pest control methods in the north resulted in greater yields, which gradually increased each year. Today, the Central Valley of California is the state’s prime walnut growing region. Its mild climate and deep fertile soils provide ideal growing conditions for the California walnut. California walnuts account for 99 percent of the commercial US supply and three-quarters of world trade.