* The Book of Flowers: A Visual History (1998)
* The Private Lives of Trees: A Celebration in Word and Image (2004)
* The Little Book of Trees: Twenty Inspiring Trees and Why They Matter (2019)
* The Art of Trees: An Illustrated Guide to the Trees of the World (2021)
Essays and articles
* "The Secret Language of Trees" (The New York Times, 2012)
* "Why We Need Trees" (The Huffington Post, 2013)
* "The World's Most Amazing Trees" (Smithsonian Magazine, 2015)
* "How Trees Can Save Us" (National Geographic, 2017)
* "The Tree of Life" (The Atlantic, 2019)
Other writings
* The Tree Museum (children's book, 2010)
* The Tree Book (coffee table book, 2014)
* The Tree Journal (guided journal, 2018)