Pecan "fruit of the walnut". They noted the particularly thin shell and acorn-like shape of the fruit, indicating they were indeed referring to pecans. The Spaniards took the pecan into Europe, Asia, and Africa beginning in the 16th century. In 1792, William Bartram reported in his botanical book, "Travels", a nut tree, "Juglans exalata" that some botanists today argue was the American pecan tree, but others argue was hickory, "Carya ovata". Pecan trees are native to the United States, and writing about the pecan tree goes back to the nation's founders. Thomas Jefferson planted pecan trees, "C. illinoinensis" (Illinois nuts), in
Juglans californica "J. californica" grows in riparian woodlands, either in single species stands or mixed with California's oaks ("Quercus" spp.) and cottonwoods ("Populus fremontii"). "Juglans californica" can be either a large shrub with 1–5 trunks, or a small, single-trunked tree. The main trunk can fork close to the ground, making it look like two trees that have grown together, then diverged. It has thick bark, deeply channeled or furrowed at maturity. It has large, pinnately compound leaves with 11–19 lanceolate leaflets with toothed margins and no hair in the vein angles. It has a small hard nut in a shallowly grooved, thick