Every March and April, the Han River valley around Hanzhong fills with rapeseed in bloom. The yellow carpets extend across the flat valley floor and up the lower terraced slopes, broken occasionally by white farmhouses, irrigation ditches, and groves of trees. Nanzheng District, Mianxian County, and Yangxian County have the most concentrated fields and the most organised viewing infrastructure; the Chencun Flower Sea in Nanzheng District is one of the more photogenic spots, with fields beside reservoirs and forested ridges behind.
The annual rapeseed festival brings significant crowds from Xi'an and further afield — mainly Chinese domestic tourists and photographers. Early morning and evening provide the best light and the thinnest crowds. If you are visiting specifically for the flowers, arrive mid-March for the valley floor in full bloom, or earlier April for the higher terraced fields. The season varies by a week or two depending on the year's temperatures.