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 hindsii ("Quercus" spp.) and Fremont cottonwood ("Populus fremontii") trees. "Juglans hindsii" has only one confirmed native stand remaining. It is listed as Seriously Endangered on the California Native Plant Society Rare Plant Inventory. The IUCN classification is a Vulnerable species. It is threatened by hybridization with orchard trees, urbanization, and habitat conversion to agriculture. "Juglans hindsii" is a medium-sized tree of short bulky proportions. It grows up to tall, has a single erect trunk, commonly without branches for , and a crown that can be wider than the tree is tall. Trunks commonly reach in diameter near the base of the