The Light Eaters

How do you describe a lifeform that builds atmospheres, retools soils, times its reproduction to neighbors, warns kin, and recruits bodyguards—without a brain? In The Light Eaters, Zoë Schlanger argues that plants are active, information-processing agents whose sensing, signaling, memory, and social strategies are central to Earth's living systems. She contends you must retire plant blindness—the reflex that treats green as backdrop—and instead see plants as decision-making networks that integrate cues across time and space.

The book blends ecology, electrophysiology, and the sociology of science to make a precise claim: agency means the capacity to sense conditions and adaptively change development (Sonia Sultan's definition). That capacity, not humanlike consciousness, explains plant feats from carnivorous trap counting to climate-scale engineering. You meet researchers whose careful methods—after decades of backlash from overhyped claims—now reveal plants communicating by chemicals, currents, light, and sound.

From backdrop to builders

Start by recalibrating scale. Plants "eat light" and exhale oxygen; they literally built the modern atmosphere. Schlanger opens with Azolla, the tiny fern whose nitrogen-fixing alliance and explosive growth helped cool the Eocene Arctic. You also visit Kaua‘i, where plants evolved in the absence of mammal herbivores and lost defenses—then suffered when new predators arrived. These cases push you to see plants as ecosystem engineers and historically contingent beings (not interchangeable resources).

A history of resistance

Western thought once dignified plants on their own terms (Theophrastus), but hierarchical views (Aristotle, then Descartes) relegated them to passive life. That intellectual backdrop primed the backlash when The Secret Life of Plants (1973) popularized fragile findings. Funding dried up; serious work on signaling and behavior carried stigma. Schlanger shows how today's revival owes less to rhetoric than to measurement—gas chromatography for volatiles, genomic tools, and fluorescent calcium indicators that let you watch signals move.

A multisensory portrait

Plants speak chemistry. Sagebrush warns kin with tailored volatile blends (Rick Karban). Tobacco and corn call parasitoid wasps to kill herbivores. Underground, roots and mycorrhizae ferry signals and resources in complex neighborhoods (the "wood-wide" context, now studied with tighter methods). They also run electricity: wound a leaf and a calcium wave fans through veins (Simon Gilroy and Masatsugu Toyota), coordinating defenses at a whole-plant scale. They feel vibrations: caterpillar chewing primes defenses (Heidi Appel and Rex Cocroft), and evening primrose sweetens nectar to bee wingbeats within minutes (Marine Veits).

Memory across timescales

Sensing turns into intelligence when it sits in time. Plants store winter in molecules (vernalization) so bulbs flower on cue. Venus flytrap counts touches before digesting. A Peruvian flower, Nasa poissoniana, remembers bumblebee visit intervals and staggers stamen lifts accordingly. These forms of memory—epigenetic, working, and interval timing—create internal states that shape future actions.

Plastic bodies, porous boundaries

Schlanger pushes beyond the single, bounded organism. Boquila, a Chilean vine, mimics several neighbors’ leaf shapes within one plant—sometimes even an introduced weed and a plastic tree. Competing hypotheses frame the mystery: distributed "vision" via leaf-surface ocelli (František Baluška, Stefano Mancuso) vs. microbial small RNAs reprogramming development (Ernesto Gianoli). Either way, you see a plant as a holobiont—host plus microbes—swapping cues and inheritance across species lines (Lynn Margulis’s lens, now grounded by microbiome science).

Core takeaway

Plants are neither passive nor simple. They are distributed intelligences—electrochemical, microbial, and architectural—whose agency shapes climate, communities, and your future choices in food, policy, and ethics.

Why this reframing matters to you

Once you treat plants as agents, practical doors open. You can design kin-aware crops that cooperate and yield more, restore microbial partners to boost resilience, or "listen" for drought via cavitation clicks. Ethically, you can extend standing to key plant communities (think White Earth Nation’s rights for wild rice) and regulate with agency in mind. And as a reader of science, you can learn the hard lesson Schlanger threads throughout: paradigm shifts depend on good instruments, careful vocabulary, and patience (compare Donald Griffin’s slow vindication in animal cognition).

In short, the book invites you to meet a different planet—one where quiet green beings plan, persuade, and persist. If you let that recognition in, your sense of responsibility expands with it.

Schlanger begins your tour of plant communication with their dominant medium: chemistry. Plants release airborne volatile organic compounds (VOCs), exude root signals, and leverage fungal partners to transmit warnings and recruit allies. Once you recognize an ecosystem as a commons of messages, you see why fragmentation, monoculture, and pollution are not just habitat loss—they’re communication blackouts.

Airborne warnings and targeted audiences

In 1983, David Rhoades watched tent caterpillars ravage trees at the University of Washington—downwind trees amped their defenses and the caterpillars died. His careful, controversial observation planted a seed: plants share airborne warnings. Rick Karban (UC–Davis) later made it robust. With sagebrush, he showed replicated, controlled field evidence that plants heed kin more than strangers and modulate "private" vs. "public" alarm channels depending on risk. That’s audience selection: akin to whispering to family while broadcasting to neighbors when needed.

Underground wires: roots and fungi

Belowground, mycorrhizal fungi link roots into exchange networks. Through these, plants move signals and sometimes resources; they bias flows to kin and allies. While the popular "wood-wide web" metaphor can outrun data, Schlanger emphasizes the maturing methods—stable isotopes, exclusion experiments—that now parse when and how these networks matter. In many systems, fungi function like community routers: passing defensive cues after attack and shaping who thrives.

Recruitment as diplomacy

Plants don’t only warn others; they recruit third parties. Tobacco and corn release VOC blends that summon parasitoid wasps to hunt caterpillars feasting on their leaves. Bittersweet nightshade pays ants with extra-floral nectar—sugar for security—patrolling leaves and removing herbivores. These are contracts with costs, benefits, and enforcement; some plants reduce rewards if partners slack, sustaining cooperation over time (think of it as ecological game theory in sugar currency).

When communications fail

Hawai‘i’s flora evolved without mammal herbivores; many species relaxed defenses. When pigs, goats, and rats arrived, plants lacked both hard defenses and tuned warning systems for these novel threats. Likewise, air pollution can oxidize or scramble VOC messages, and monocultures erase diverse signal vocabularies. The result is predictable: more pest outbreaks, more pesticide reliance, and fewer natural buffers.

Practical takeaway

Treat interplant signaling as infrastructure. Diversify plantings, preserve mycorrhizae, and harness VOC lures (e.g., parasitoid recruitment) to reduce chemical inputs and stabilize yields.

Evidence that persuaded skeptics

Baldwin and Schultz replicated airborne signaling in controlled chambers, helping erase the stigma attached to early field claims. Even anecdotal stories—like Wouter van Hoven’s kudu deaths when acacias spiked tannins under heavy browsing—became prompts for rigorous tests of tree-to-tree coordination. The arc is instructive: early, messy signals invite skepticism; better instruments and replication convert the idea into accepted ecology.

Once you accept that plants coordinate through chemical and fungal networks, you begin to see landscapes as choral, not silent. Your management lens shifts from isolated individuals to neighborhoods of talkative, risk-sensitive partners.

If chemistry is the language of neighborhoods, electricity is a plant’s rapid internal courier. Schlanger shows you how plants generate electrical spikes and calcium waves to integrate local damage into whole-body decisions—without neurons. This isn’t a metaphor borrowed from animals; it’s a parallel solution to moving information through living tissue.

From Bose to fluorescent waves

A century ago, Jagadis Chandra Bose inserted microelectrodes into plants and recorded voltage shifts. Skeptics dismissed the work as curious. The story restarts with modern tools: genetically encoded calcium sensors light up when calcium surges. In 2018, Masatsugu Toyota and Simon Gilroy cut a leaf and watched, on a screen, a green fluorescence wave zip along veins across the plant. Add glutamate and the wave accelerates to roughly a millimeter per second—far too quick for slow chemical diffusion, consistent with excitable membranes propagating signals.

Action potentials and counting

The Venus flytrap is the showpiece. Touch a trigger hair once: nothing. Twice within a short window: snap shut. Then, only after additional action potentials does digestion begin. This is a timed, counted decision—an energy budget enforced by electrical arithmetic. Earlier, John Burdon-Sanderson and others mapped these spikes; now, molecular tools link the waves to hormonal cascades that mobilize defenses or metabolism (e.g., proteinase inhibitors after wounding, shown by Wildon et al. in the 1990s).

Neurochemical parallels, not neurons

Plants use glutamate-like receptors and calcium as second messengers—molecules familiar from neuroscience. But they do not have neurons or synapses as animals do. Schlanger stresses function over homology: similar parts can build different architectures that still compute. Think distributed networks of excitable cells that sum and route signals through vasculature and membranes.

Anesthesia and the "consciousness" thicket

Anesthetics can halt Mimosa leaf-folding and freeze Venus flytrap responsiveness, blocking electrical integration. František Baluška calls this plant "unconsciousness"; critics counter the term misleads without a brain. Schlanger’s middle path: anesthesia reveals how crucial bioelectric integration is to plant behavior, but you shouldn’t import human consciousness claims (compare debates around Integrated Information Theory).

Key image

A wounded leaf lights up with a traveling green halo—calcium and charge moving like a message from fingertip to body, telling distant tissues to prepare.

Why it matters to you

Once you see electrical waves coordinating plant responses, you have a mechanistic substrate for plant decisions, memory, and rapid behavior. In practice, electrophysiological readouts could become early-warning tools in agriculture—detecting stress before symptoms show. Conceptually, this reframes plants as real-time integrators of information, narrowing the gap many assume separates them from animal-like responsiveness.

The lesson is methodological, too: careful terms ("electrical signaling" instead of "plant neurons") keep the science grounded and fundable, even as it challenges old categories.

Plants inhabit a sonic ecology you rarely notice. Schlanger introduces phytoacoustics—the study of how plants detect, discriminate, and react to vibrations and airborne sound. Here, plants prime defenses to caterpillar chewing, sweeten nectar to bee buzzes, and perhaps eavesdrop on drought through ultrasonic clicks. Sound becomes another channel in the multisensory plant web.

Chewing, buzzing, and rapid rewards

Heidi Appel and Rex Cocroft captured the exact vibration signature of caterpillars chewing leaves. When they played those vibrations to Arabidopsis, the plants boosted chemical defenses—without a single bite. That’s a clean, reproducible demonstration: the sound of danger primes immunity. Marine Veits and colleagues showed evening primrose detects bee-like wingbeat frequencies and raises nectar sugar within minutes, essentially advertising to nearby pollinators with a tastier payout.

Antennas and transducers

How do plants "hear"? Leaf hairs (trichomes) vibrate and focus energy like tiny tuning forks; mechanosensitive channels transduce movement into calcium signals and hormonal cascades. Shape matters: Lilach Hadany’s group showed the flower bowl can resonate at bee frequencies, amplifying useful input (form and frequency coevolve, as with bat-pollinated leaves shaped to reflect sonar).

Contested findings and careful curiosity

Monica Gagliano reported pea roots growing toward the sound of running water and even plant associative learning. Some replications failed, and her blending of Indigenous and laboratory methods unsettled peers. Schlanger threads a balanced view: bold questions expand the horizon; reproducibility and field relevance must settle the claim. Meanwhile, new work by Itzhak Khait and others suggests drought-stressed plants emit ultrasonic "clicks"—cavitation events in xylem that might be informative to neighbors, herbivores, or fungi.

Important implication

If you can prime plant immunity or pollination with sound, farms could reduce pesticides and increase yields with nonchemical inputs—provided the sound "recipes" scale and remain species-specific.

What to try and what to avoid

Expect frequency specificity: random noise won’t help, and the wrong band could stress plants. Field trials must confirm that lab-demonstrated effects persist amid wind, insect choruses, and machinery. The promise is real but early—stay curious, demand replication, and watch how acoustic tools pair with electrophysiology to "listen" to plant state in real time.

Viewed alongside chemical and electrical channels, acoustics rounds out a picture of plants as multimodal listeners, parsing a busy world to act quickly and economically.

A one-off reflex doesn’t make a mind; memory does. Schlanger argues that when plants keep internal records—molecular or electrical—that persist beyond a stimulus, they cross into decision territory. The evidence spans seasons to seconds, from bulbs counting winters to traps counting touches.

Seasonal records: epigenetic memory

Vernalization encodes cold exposure so plants flower at the right time. In garlic and other bulbs, prolonged chill leaves chromatin marks that switch on flowering genes months later. Sonia Sultan’s work shows parental environments tune offspring: droughted parents yield seedlings with deeper roots; shaded parents deliver children that stretch early and tall—changes that can persist across generations through epigenetics and maternal provisioning (and likely microbial legacies).

Working memory: counts and windows

The Venus flytrap’s arithmetic is working memory in action. It tallies action potentials within a narrow time window before committing energy to a costly digestive process. Dodder vines appear to track coiling attempts around a host, adjusting investment as they secure attachment—another plausible example of short-term tallying tied to payoff (a behavior that invites further quantification).

Timing behavior to partners

Nasa poissoniana flowers in the Peruvian Andes memorize the typical interval between bumblebee visits. When researchers probed at 15- vs. 45-minute intervals, the plant adjusted stamen lifts to match. That’s not a simple stimulus-response; it’s interval timing—a statistical memory of recent visit patterns used to maximize pollen transfer.

Why memory narrows the gap

Memory implies an internal state that shapes future behavior. Whether stored in chromatin, ion channel states, hormonal circuits, or microbial context, those states give plants a subjective history. Your narrative memory feels different, but functionally, both let organisms integrate past with present to decide. In sessile life, timing is everything: remember frost and wait; remember bee cadence and synchronize; remember last bite and toughen up.

Applied lesson

Plant pasts are programmable. Manage parental environments and microbial partners to "pre-adapt" crops to drought, heat, or shade—an eco‑devo path that complements genetics.

Seen through this lens, learning stops being binary and becomes a spectrum—from gene regulation that "remembers" winter to electrical counters that decide a meal is worth the cost. The practical and philosophical distance between you and a shrub gets smaller, not by metaphor, but by mechanism.

Vision sounds like eyes, but biology defines it as perceiving light’s qualities and directions. Plants already do that exquisitely: they bend toward light, detect neighbors by red/far‑red ratios, and even recognize kin as light filters through related leaves (Crepy & Casal). Schlanger takes you further, into a debate about whether plants possess distributed ocelli—simple, non-photosynthetic light sensors on leaves—and how that might solve a spectacular puzzle: Boquila’s chameleon leaves.

Photoreceptors and spatial inference

Plants carry a suite of photoreceptors (phytochromes, cryptochromes, phototropins, more) that record wavelength, intensity, and duration. Dodder seedlings use far‑red signatures transmitted through plant tissue to discriminate branched woody hosts from grasses—essentially reading shape from light quality at a distance. Cyanobacteria, chloroplasts’ ancestors, act like microlenses; they focus light to steer—an evolutionary hint that complex light-sensing architectures without eyes are plausible.

Enter Boquila trifoliolata

In Chile’s temperate rain forest, Ernesto Gianoli and Fernando Carrasco-Urra found a vine that mimics the leaf shape, color, texture, and even vein pattern of many hosts—within a single plant’s lifetime. One segment throws large, fingerlike leaves to match a tree; another produces tiny, rounded leaves to match a nearby shrub; another imitates an introduced weed present for less than a decade. Boquila even mimicked a plastic tree planted by a gardener (as reported by Baluška and Mancuso)—if reproducible, that strains explanations requiring genetic exchange.

Two live hypotheses

Baluška and Mancuso propose leaf-surface ocelli—specialized epidermal cells that detect light patterns and reconstruct neighbor geometry and color (reviving Gottlieb Haberlandt’s 1905 idea). Distributed across the plant, they could perceive from multiple angles, potentially explaining subtle feats like copying an underside spike on Rhaphithamnus spinosus leaves that Boquila reproduces. Gianoli leans microbial: host-associated bacteria colonize adjacent Boquila leaves and carry small RNAs or cues that reprogram leaf development. His team found the microbiome on mimicking Boquila leaves resembled the host’s far more than Boquila leaves elsewhere on the same vine.

How to test the riddle

Boquila resists greenhouse cultivation, slowing progress. But decisive tests exist: grow Boquila sterile near artificial leaves to favor the vision model; or swap microbial communities between Boquila leaves and track mimicry outcomes to favor microbes. Knock out specific photoreceptors and see if color or shape copying fails; identify ocelli-like cells with directional sensitivity. Each step clarifies whether plants see with non-eyes, morph via microbes, or—most likely—blend both.

Deeper point

Boquila collapses the tidy border between organism and environment. Whether by light-sensing tissues or borrowed microbes, the plant’s identity becomes a dynamic readout of context.

The riddle’s value exceeds its answer. It forces you to entertain organismal porosity—an idea that reverberates through holobiont inheritance, kin signaling, and the ethics of treating plants as isolated "things."

Plants don’t live alone; they manage relationships. Schlanger gathers evidence for kin recognition, cooperative neighborhoods, and microbe-mediated inheritance to argue that social and ecological context is part of a plant’s body plan. When you farm or conserve, you’re shaping societies, not just species.

Kin recognition in action

Susan Dudley’s work with American searocket showed seedlings restrain roots among kin but forage aggressively near strangers—resource conflict dialed by relatedness. Impatiens rearrange leaves to avoid shading siblings. Arabidopsis detects kin via light filtered through related leaves and adjusts angles to reduce overlap (Crepy & Casal). These are context-sensitive rules you can exploit.

Cooperation that pays

In a striking study, related sunflowers tilted in alternating patterns, reducing mutual shade and boosting oil yield by up to 47%. In rice, Chui‑Hua Kong found root expansion scaled with genetic distance; blocking chemical exudates erased kin effects, revealing underground signaling as the mediator. Kevin Burns even describes staghorn ferns forming colonies where some fronds act like sterile workers feeding reproductive fronds—a plant analogue of eusocial division of labor (a provocative comparison, not identity).

Coexistence vs. constant war

JC Cahill’s long-term grassland work shows plants often avoid costly head-to-head fights when alternatives exist—"polite foraging." But flexibility cuts both ways: under scarcity, plants pull allelopathic levers and compete hard. The point is repertoire, not saintliness. Social rules shift with conditions, and management that stabilizes resources can promote cooperative equilibria.

Holobionts: inheritance beyond genes

Lynn Margulis’s holobiont frame becomes practical here. Parents pass microbes, small RNAs, and epigenetic marks that preload offspring for expected environments (Sonia Sultan’s eco‑devo). Droughted lineages deliver deeper-rooted seedlings; shaded lineages pre-arm for low light. Gianoli’s Boquila data suggest even leaf microbiomes can shape development locally, hinting that part of "who you are" arrives from neighbors.

Actionable shifts

Breed for group performance, not lone-wolf vigor; plant kin-aware blocks; protect and inoculate with beneficial microbiomes; and track multi-generational effects when testing varieties.

When you accept plants as social holobionts, agriculture looks less like maximizing an individual plant’s horsepower and more like tuning a team—roots, fungi, microbes, and neighbors—to the field’s changing score.

Plants negotiate constantly—with animals, microbes, and us. Schlanger closes by showing how plants recruit, bribe, and deceive across species lines; how agency drives invasions; and how scientific fields inch from ridicule to respect when methods catch up with claims. You come away with ethics and policy questions you can’t ignore.

Persuasion across species

Tomatoes and tobacco call in parasitoid wasps; bittersweet nightshade pays ants to patrol. Australian orchids synthesize pitch-perfect analogs of female-wasp pheromones, luring males into pseudocopulation that spreads pollen (Rod Peakall). And in a twist, bumblebees bite mustard leaves to force earlier flowering (Consuelo De Moraes), manipulating plant timing for their own scarcity problem. These are not one-way "signals"; they are negotiations where both sides shape outcomes.

Agency and the invasion lag

Sonia Sultan reframes agency as measurable plasticity and developmental choice. Her studies of Polygonum cespitosum (smartweed) show lineages rapidly evolve "super-plasticity," then pass adaptive states to offspring—explaining why invasions often explode after a quiet lag. Japanese knotweed demonstrates the social and legal shock of such agency: it spreads rhizomatically, resists control, and even affects property markets.

Law, rights, and responsibilities

If plants demonstrate agency in the wild, what moral and legal standing do we grant them? Christopher Stone asked if trees should have standing; the White Earth Band recognized rights for wild rice (manoomin). Trewavas doubts culture will pivot fast, but Schlanger sees traction in pairing Indigenous philosophies—plants as kin—with pragmatic legal instruments that protect ecosystems upon which human futures depend.

How science turns

Kuhn’s paradigm story runs through the book. After The Secret Life of Plants tainted the field, progress required better tools and cautious language: volatile assays that replicate, calcium imaging that visualizes waves, and field manipulations with controls. Personalities matter: Rhoades’s career collapsed; Karban, Baldwin, Schultz, Gilroy, and Toyota triumphed with design rigor and timing. The meta-lesson for you: pick testable hypotheses, coin careful terms ("behavior" before "intelligence"), and let instruments do the persuading (as in Donald Griffin’s long road for animal minds).

What to do next

Design companion plantings that exploit natural alliances; screen genotypes for plasticity and cooperative traits; regulate introductions to curb invasion risk; and consider rights-based protections for keystone plant communities.

Seen end to end, Schlanger’s case is not mystical. It’s a call to widen your map of agency and accountability—to treat plants as the sophisticated partners they are, in science, on farms, and in law.