"I've got some health problems, but I don't feel sick when I paint and can work for about nine hours a day. I finished some 130 paintings during this time," he said.

Zeng started his career as a natural history illustrator at the Kunming Institute of Botany affiliated with the Chinese Academy of Sciences in 1958. He participated in the compilation of the "Flora of China," a publication composed of 126 volumes, which records more than 31,000 species of plants. The huge project took 45 years to complete.

After retirement, Zeng started to give more emphasis to the artistic aspect of his creations and has kept honing his skills.

"I've never drawn something that I'm completely satisfied with. I always said to myself that if only I could do it better when I finish one piece," said Zeng. "All plants have life and life is the hardest thing to depict."

In fact, his works have been well-received by the public.

"I'm so impressed. I can enjoy beautiful details of the plants that I've never noticed and feel their great vitality," said Li Li, a local resident.