NPR interviewed Walter Judd, a retired botanist, about his book Flora of Middle-Earth. From their article:
" 'I started underlining every name of a plant as I was reading The Lord of the Rings,' he tells NPR's Morning Edition.
Moved by Tolkien's passion for plants, the retired botany professor spent years cataloging every plant that appeared in his writing, eventually compiling a list of 141 different species. He teamed up with his son, Graham, a professional illustrator. And together, they embarked on quest to transform that list into a botanical guide to Middle Earth."