Walnuts in California

Walnuts are an indigenous fruit species of California. Juglans californica is native to Southern California and the Central Valley, whereas Juglans hindsii is native to the northern parts.

Franciscan Fathers first introduced the English walnut around the 1770s from South America to California. As of 1998^[update], walnuts from California account for 99% of all walnuts grown in the United States, and for 38% of the world's production of walnuts.

Black walnuts are an important foodstuff for indigenous Californians, including the Yokuts, who also use the hulls in their traditional dice. Hot asphaltum is poured into the empty shells, then pressed with beads made from Olivella sp. or abalone shell.

The first walnut orchard to be planted by Europeans in California was in 1856, by Ozro W. Childs, in what is now the center of Los Angeles. William Wolfskill, who is considered the founder of the first commercial orange orchards in California, also planted hard-shell English walnuts in the Los Angeles Area. Other early walnut growers of both hard- and soft-shell varieties include Russell Heath, Frank E. Kellogg and William Huston Nash, and W. E. Stuart.

In the winter of 1869, Joseph Sexton planted the first known commercial walnut orchard in Goleta, California, after purchasing a bag of English walnuts in San Francisco that he was told were from Chile or China, no one knows for certain. This orchard contained 1000 trees, of which 250 were part of Sexton's personal orchard. Around the same time in 1870, Felix Gillet, a nurseryman in Nevada City, California, was importing scion wood and nursery stock from France. Gillet is credited with introduction of Franquette and Mayette cultivars to California, as well as other French cultivars. Gillet established his orchard in Northern California in 1871. He grafted and budded the French cultivars for commercial use and used a selection program for his seed to cultivate new varieties of walnuts suited for California. Many of the varieties of the walnuts grown in California were introduced by Gillet and Sexton; out of 35 varieties, the 7 varieties they introduced from seedlings and selections make up 82 percent of total walnut acreage.

From 1879 to 1885, Luther Burbank conducted the first walnut breeding experiments, observing that walnut species easily fertilized with each other. He observed that the hybrid walnut trees were more vigorous that either parent trees. Burbank gave name Royal to hybrids between eastern American black walnuts (J. nigra) and northern California black walnuts (J. hindsii). He also named hybrids between north California black walnuts and English walnuts (J. regia) "Paradox". Growers eventually accepted that the Paradox hybrids had superior attributes being more vigorous and disease resistant to crown and root rot.

A modern-day variety of walnuts grown California is the Serr walnut, developed by UC Davis professors Eugene F. Serr and Harold I. Forde. From 1945-1968, their extensive walnut-breeding program created seedlings which exhibited desirable traits such early production, moderate tree vigor, pest and disease tolerance, and high nut quality. From 1,734 controlled cross walnut seedlings, Serr and Forde selected 10 new English walnut varieties for release in 1968. The Serr variety (named after Serr's death in 1968) now occupies 23,667 acres, or 12 percent, of California walnut acreage. Other varieties selected were Tehama, Gustine, Chico, and Vina. Forde continued making specific crosses and progeny evaluations until retiring in 1978. His persistence resulted in the release of four more Serr-Forde selections: Chandler, Howard, Sunland, and Tulare. The Chandler variety, a late-leafing, lateral-bearing walnut is very popular with California walnut growers. It represented 75 percent of nursery stock delivered in 1993.

With the expansion of the walnut industry, growers soon experienced problems in marketing their crop. The rapid increase in acres planted to walnut and lack of organization resulted in prices fluctuations and buyers unfairly competing with one another for commissions. In 1933, the Walnut Marketing Board was formed under the Agricultural Adjustment Act, to oversee quality control and marketing of the walnut in California. To this day the Walnut Marketing board is responsible for implementing the federal marketing order for California walnuts. To emphasize its role in managing the walnut market, the Walnut Control Board changed its name in 1962 to the Walnut Marketing Board. To further promote the export of walnuts, the California Walnut Commission was created in 1987 the governor of California. The commission differs from the Walnut Marketing Board, which by a federal order is responsible for standards, statistics, crop estimates, research, and domestic marketing.