Photo taken on April 9, 2020 shows flowers in the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region . (Xinhua/Zhou Hua)

Aerial photo taken on April 9, 2020 shows a view of the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region. (Xinhua/Cao Yiming)

Aerial photo taken on April 9, 2020 shows a view of the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region. (Xinhua/Cao Yiming)

Aerial photo taken on April 9, 2020 shows a view of the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region. (Xinhua/Cao Yiming)

Aerial photo taken on April 9, 2020 shows a view of the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region. (Xinhua/Cao Yiming)

Aerial photo taken on April 9, 2020 shows a view of the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region. (Xinhua/Cao Yiming)

Black swans are seen at the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region, April 9, 2020. (Xinhua/Cui Bowen)

Black swans are seen at the Nanning Garden Expo Park in Nanning, south China's Guangxi Zhuang Autonomous Region, April 9, 2020. (Xinhua/Cui Bowen)