Author: Zoe Schlanger
Published: 2024, Harper
Pages: 304 in hardcover edition
Completed: February 2025
Nonfiction
Genre or topic: botany, plant physiology, popular science
Why read this? If you’re a gardener or houseplant lover or just interested in natural history, you’ll probably be fascinated to learn (more) about how plants interact with each other and their environment. It will help you understand the latest science on what at least some scientists believe plants are capable of, much of which surprised me. This book made several 2024 “best of” lists for nonfiction books, including those by The New Yorker, Amazon, Time and The Smithsonian. I’m glad I read this book and recommend it.
Why not read this? This may not be a good pick right now if you’re in the early stages of rebuilding your ability to focus on reading books and other long-form content, because it’s quite information-dense. I therefore found it required a level of concentration higher than that for reading fiction or just nonfiction that’s less fact and research heavy. Quite a few of the botanical, plant physiology and chemistry discussions were over my head and I ended up skimming some of those parts. This all meant that the book took me a while to complete. If you’re the same, this slow progress may discourage you and contribute to a reading slump. There were a few places where Schlanger made political comments that I found preachy and therefore somewhat annoying, but it was easy to overlook these. Also, she spends quite a bit of time discussing the nitty gritty of academic disputes between plant scientists over the finer points in their research findings. This is not to say these debates, e.g., over what does or does not constitute plant “intelligence” or “communication” aren’t important – such challenges and how they are responded to are how scientific knowledge is built and in this case, also have ethical implications. But the extent of detail may be more than holds the interest of most lay readers. I do still recommend the book.
Here are some of the insights and new information I learned from reading the The Light Eaters:
Schlanger explains that academic research into the field of plant behaviour underwent a long fallow period after the 1973 publication of the bestselling book, The Secret Life of Plants, which she describes as “a mix of real science, flimsy experiments, and unscientific projection.” the book included suggestions that plants could not only hear music, but preferred Beethoven to rock music and were capable of reading our minds. It was considered a scandal and funding bodies and peer review boards reacted by turning off the money taps for about three decades after this.
Schlanger describes plants as having been forced, by the fact of their immobility and vulnerability to predators, to “engineer some of the most impressive adaptations in nature,” and most significantly, modularity. When you trim a plant’s stem or leaves, or cut off a flower before it sets seed, plants respond by growing more of these parts – something humans are not able to do. Lacking central nervous systems, the essential organs of a plant are distributed throughout its “body” and often come in twos – which has allowed plants to develop elaborate and precisely targeted ways to protect themselves from predators, e.g., thorns that are perfectly suited to puncture the flesh of its primary predators.
- For example, “Several species of plants have been found to identify a caterpillar’s species by sensing the compounds in its saliva, and then synthesize the exact compounds to summon its predator. Parasitic wasps then obligingly arrive to take care of the caterpillars.”
- In another case, the scientist David Rhoades found that (willow) trees adjusted the content of their leaves in response to being devoured by tent caterpillars – in a way that caused the caterpillars to die of diarrhea. Further, this change in the leaf content took place not only in trees that had been subject to the onslaught, but in those (of the same type) that were unaffected, including those too far away to allow for root communication. This suggested that the trees had communicated via chemicals through the air. “The idea that a plant would actively defend itself, though, was heretical to the whole premise of how scientists thought plants worked. Plants were not supposed to be that active, or have such dramatic and strategic reactions.”
- In another example, goldenrod plants in areas where they are predated upon rarely were found to send “chemical alarm calls” that only their closest relatives could understand, whereas goldenrod in areas where threats are common were found to use chemical warning signals that all the goldenrod plants could understand – suggesting that those living in higher threat areas had adapted by developing a broader community and that they were aware enough of their surroundings to know how and when to use different communication strategies.
- In 2006, a group of established scientists started the Society for Plant Neurobiology, and “called for the pursuit of the idea of plants as intelligent beings, in the sense that they could process multiple forms of information to make well-informed decisions.” They later renamed themselves to the less controversial Society for Plant Signaling and Behaviour.