Photo taken with a mobile phone shows a view at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows a view at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)

Photo taken with a mobile phone shows blooming flowers at the 2019 Beijing International Horticultural Exhibition (Expo 2019 Beijing) in Yanqing District of Beijing, capital of China, May 9, 2019. (Xinhua/Wei Mengjia)