This so-called "English Walnut" is really native to central Eurasia. The species is widely cultivated across North America, including Ky. It may escape in Pacific states and the Great Lakes area (K), but there are no such records from Ky. It is in section Juglans, and differs from the East Asian species (section Cardiocaryon) as follows (Flora of China 4): leaflets glabrous on lower surface except in axils of midvein and secondary veins (versus pubescent or rarely glabrescent), margin entire to minutely serrulate (versus serrate or rarely serrulate); nuts 4-chambered at base (versus 2-); husk irregularly dehiscent into 4 valves (versus indehiscent); shell wrinkled or smooth ridged and deeply pitted (versus rough ridged and deeply pitted)