A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)

A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)

A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)

A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)

A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)

A farmer works in a greenhouse in Tai'an County, northeast China's Liaoning Province, May 12, 2020. Tai'an has been encouraging farmers to grow fruits and vegetables in greenhouses as a way to increase incomes. (Xinhua/Yao Jianfeng)