The flower, preferred by royal families for its luxuriant blossoms, symbolises prosperity and wealth.
The "peony king" is over 120 years old and measures 2.7 meters tall and 3.7 meters wide.
"The shape of the branches looks natural but compelling, and the flowers are gorgeous," said a tourist, Wang, who came from east China's Jiangxi Province to see the city's flowers.
China's "city of peonies" has attracted tourists from across the country, state run Xinhua news agency reported.
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Once the imperial capital of 13 dynasties, Luoyang is home to the country's best peony trees.
The city holds an annual festival to celebrate the blooms.
This year's event kicked off earlier in April.
The Moutan or Chinese tree peony is a species of peony native to China. They are long-lived, hardy shrubs provided they are grown in a suitable spot. The common name is misleading as they are not trees but deciduous shrubs.