In 1920 Rock left Hawaii for what would prove to be decades of residence and expeditions in Asia, mostly in Western China. The U.S. Department of Agriculture employed him as an agricultural explorer, sending him to Southeast Asia in search of seeds of the Chaulamoogra tree (Hydnocarpus wightianus), which was used in the treatment of leprosy. This success led to further expeditions in Southwest China, and in 1922 Rock first arrived in Lijiang in the northwest of Yunnan province, the center of the Nakhi (Naxi) people. The valley of Lijiang is dominated by the Yulong (Jade Dragon Snow Mountain) range, at whose foot Rock established a residence in the village of Nguluko. This would be his primary base for the next 27 years, as he organized botanical expeditions throughout much of western China along the eastern borderlands of Tibet, a large, remote and very rugged area with numerous non-Han peoples for the most part only nominally governed by the Chinese government. Throughout the period Rock was in China, the country was wracked by warlordism, civil war, the war with Japan and finally the triumph of Mao Zedong's communist forces. Western China was parceled out into a colorful array of petty states and tribal territories, and infested with banditry, a well established way of life throughout these areas.