Juglans regia, the Persian walnut, English walnut, especially in Great Britain, common walnut, or especially in the US, California walnut, is an Old World walnut tree species native to the region stretching from the Balkans eastward to the Himalayas and southwest China. The largest forests are in Kyrgyzstan, where trees occur in extensive, nearly pure walnut forests at 1,000–2,000 m altitude (Hemery 1998)—notably at Arslanbob in Jalal-Abad Province.