Undated photo shows farmers enjoy the marigold flowers harvest in Songshu Town of Qingshui County, northwest China's Gansu Province. (Photo: China News Service/Wang Weidong)

Undated photo shows farmers pick marigold flowers in Songshu Town of Qingshui County, northwest China's Gansu Province. (Photo: China News Service/Wang Weidong)

Undated photo shows a farmer picks marigold flowers in Songshu Town of Qingshui County, northwest China's Gansu Province. (Photo: China News Service/Wang Weidong)

Undated photo shows farmers transport freshly picked marigold flowers to the acquisition base in Songshu Town of Qingshui County, northwest China's Gansu Province. (Photo: China News Service/Wang Weidong)

Undated photo shows a view of marigold flower fields in Songshu Town of Qingshui County, northwest China's Gansu Province. (Photo: China News Service/Wang Weidong)