Photo taken with a mobile phone shows flowers at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows people visiting the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows a scene at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows a scene at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows a scene at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows a scene at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)

Photo taken with a mobile phone shows a scene at the Beijing International Horticultural Exhibition in Beijing, capital of China, on June 3, 2019. (Xinhua/Ding Jing)