He also took an interest in the forest flora of northwest and central India and of Indian trees in general. Even after retirement, Brandis continued to work on Indian forestry, and at the age of 75, he started his principal botanical work, "Indian Trees", dealing with 4400 species. It was first published in 1906 and re-issued several times afterwards, the last time in 1971. He was posted at Balaghat in M.P. as a principal of forester training institute for a long time in his service period.