Xiang says in his nearly 30 years of editing experience, Zhou's book is the largest project he has worked on, as well as for many of his other colleagues.

"We designed a catalogue for the over 5,000-page book series and made an index based on the Latin name of the plants to make the book more practical for readers," Xiang says.

"The field work was quite arduous," Xiang says, adding that once Zhou got better pictures of the plants included in the book, he would ask the team to replace the photos, even right before the book was to be printed.

All of the over 13,000 photos used in the book series were taken by Zhou, selected from his 350,000 photos.

Xiang says there are around 2,000 medicinal plants in Northeast China, and Zhou's book covers around 95 percent.