Zen Mind, Vegetal Mind

Paco Calvo was dismayed. The prominent plant scientist had traveled to Dharamsala with a group of researchers to meet His Holiness the Dalai Lama. During a reception, Calvo had the opportunity to present his recent book, Planta Sapiens, which compiles the latest data on plant behavior, to argue that plants are sentient—that they feel pain and pleasure, make choices, and experience reality much the way humans do.

As Calvo recalls, the Dalai Lama looked shocked.

“No, no…” Calvo remembers him saying. “That is not right. Plants are not sentient.”

Calvo was surprised. Buddhists, he had assumed, espoused a kind of nondualism that might make them amenable to his research. Now he wasn’t sure. What evidence, Calvo wondered, might resonate with His Holiness?

During his visit, Calvo learned about the importance of compassion within Tibetan Buddhism; the Dalai Lamas are believed by Tibetan Buddhists to be manifestations of Avalokiteshvara, or Chenrezig, the bodhisattva of compassion. Inspired, he began compiling studies that observe altruistic behavior in plants: that they share nutrients and seem to make sacrifices for the betterment of others. Then, on his flight back to Europe, Calvo read a copy of the Dalai Lama’s book Beyond Religion, which His Holiness had gifted each scientist before their departure. Calvo felt a jolt of excitement when he reached page twenty-two, where he underlined the following passage:

During one of my many discussions with my late friend, the neurobiologist Francisco Varela, we talked about what it is that distinguishes sentient forms of life from plant forms of life. As I recall, he suggested as a criterion “an entity’s ability to move itself from here to there,” or words to that effect. If an organism can move its whole body from one place to another to escape danger and survive, or to obtain food and to reproduce, then it may be regarded as a sentient being.

Calvo knew he could satisfy this criterion. He searched for the time-lapse video of a bean plant spiraling up and out as it reached toward a pole. The scientist felt hopeful that, presented with evidence of altruism and movement, His Holiness might permit plants into the realm of beings who suffer, crave, and care.

Plants have recently captured public imagination, fueled by a surge of research into their sophisticated behaviors. Scholars like Suzanne Simard, Robin Wall Kimmerer, Stefano Mancuso, and Monica Gagliano have mainstreamed notions that years ago may have seemed preposterous: that plants communicate, signal, sense, and cooperate in ways previously unimaginable. The popularity of books like The Secret Life of Trees and Entangled Life speak to a moment in which humans are looking to be inspired by the intelligence of our “more-than-human” kin.

Experiments reveal, for example, that plants use a complex molecular vocabulary to signal distress, deter enemies, and recruit animals to perform services for them. One study found that the caffeine produced by many plants may function in some cases as a psychoactive drug that encourages pollinators to remember a particular plant and return to it, like faithful regulars frequenting a savvy neighborhood coffee shop. Other plants recruit botanical “bodyguards” to defend them from pests. When attacked by caterpillars, lima bean and corn plants emit a chemical SOS. Faraway wasps follow the call to the threatened plant to ward off the enemy. But plants also display acts of cooperation and care. They can recognize kin and nurture their young. Some trees nourish their shaded seedlings until they grow tall enough to reach light.

This research, however, remains controversial. The problem isn’t necessarily the data, but rather how scientists interpret them and the language they use to do so. Skeptics regard these studies as evidence of nothing more than instinct. Plants are mechanically hardwired to react to stimuli in predetermined ways. But others believe these findings to be proof of intelligence: to use Calvo’s definition in Planta Sapiens, behavior that is adaptive, flexible, anticipatory, and goal-oriented. Some even argue that plants are sentient or conscious, meaning they have a subjective experience of reality. They feel pleasure or pain much like you and me. However, many scientists disagree.

Framed by bioscience, these debates may seem patently modern. But Buddhists have grappled with similar questions for millennia. How should we regard the life of a plant? What possibilities do we afford to beings understood as sentient versus those that are insentient? The answers to these questions undergird Buddhist ethics, metaphysics, and soteriology (who can achieve liberation). After all, only sentient beings are considered subject to the laws of karma and transmigrate the six realms through samsaric rebirth. If plants are sentient, might a maple tree have been my mother in a past life? Could I be reborn as a blade of grass?

Not only do plants have a spiritual life, they are the spiritual life.

As a Zen Buddhist, I regard these questions not simply as theoretical issues to be determined by doctrine but as lived inquiries illuminated through practice. I have long felt a profound kinship with plants, one that first called me to a decade-long career in environmental policy and, most recently, into graduate work at Harvard Divinity School. There, I lead Harvard’s campus wide “Plant Consciousness” reading group, which gathers students from across the humanities, arts, and sciences to reflect on the latest research surrounding plant minds. As I review compelling modern science and ancient debates, I find myself asking: What changes about my Buddhist practice if I acknowledge that plants may have minds, or even a kind of spiritual life?

Questions about the nature of plant life have divided Buddhists throughout history. Like all religions, Buddhism is internally diverse and has evolved over time. What we do know is that the earliest Buddhists in India were surrounded by forests, fields, and flowers. It is no wonder that they, like us, pondered the inner lives of these ubiquitous beings. But unlike their Jain or many Hindu contemporaries, they did not clearly understand plants as sentient. The Pali canon is indeterminate at best on the topic. For example, according to ethical guidelines for ascetics (the Vinaya), monks and nuns are not to fell trees, destroy seeds, harvest palmyra palms, or trample grasses as they collect alms. Since mango, banyan, lotus, and jasmine require nonharm, we might be tempted to assume they were regarded as sentient beings. In some cases, the Vinaya seem to characterize plants as “one-facultied [beings]” (ekindriya) endowed with the sense of touch (kaya). This suggests that, like scientists today, early Buddhists mapped observable plant behavior onto human categories, determining they were like us enough to warrant the ahimsa (nonharm) afforded to more obviously sentient beings. Elsewhere in the scriptures, the Buddha states that he would declare sala trees “stream-enterers” if they were able to comprehend his teachings—implying that they can’t. But both the Metta Sutta and the Sutta Nipata include plants as beings toward which one should cultivate benevolence. Yet what happiness could we hope for beings supposedly devoid of pleasure, pain, and a desire for awakening? Considering these ambiguities, scholars suggest that plants in earliest Buddhist texts represent “borderline beings,” marking the boundary between sentience and insentience—much as they do today in scientific disputes.

This boundary assumed a central role in later debates beginning in the 6th century in China and later in Japan. The question of plant sentience exemplified a broader tension within the foundational tenets of Mahayana Buddhism. At stake was not only plants but the whole material world. Scriptural sources like the Saddharmapundarika Sutra and the Mahaparinirvana Sutra made clear that buddhanature is universal to all beings, and that by virtue of buddhanature, all sentient beings will attain enlightenment. But if everything possesses buddhanature, why are only sentient beings able to awaken? What are the bounds of sentience? If rocks, roof tiles, and chrysanthemums possess buddhanature, could they not also achieve liberation?

These debates are complex, varied, and resist simple summary. Some scholars maintained that only sentients, excluding plants, could make progress toward becoming a Buddha because only sentients had “mind.” Others avoided this tautology by rethinking the category of “mind” altogether. For example, Tiantai scholars—a school of Buddhism that emphasizes, among other things, universalism and unity—challenged the idea that buddhanature arises from an individual cognition that is situated squarely between our ears (or stems).

Foreshadowing recent trends in the study of consciousness toward “panpsychism”—which holds that “consciousness is a fundamental and ubiquitous feature of reality” (Galileo’s Error, 2019)—they argued that buddhanature pervades all phenomena. Chan-jan (711-782), a Chinese Tiantai patriarch, exemplifies this conviction when he declares:

Therefore, we may know that the single mind of a single particle of dust comprises the mind-nature of all sentient beings and buddhas . . . when we speak of all things, why should exception be made in the case of a tiny particle of dust? Why should the substance of [buddhanature] pertain exclusively to “us” rather than to “others”? … there is only one undifferentiated nature. 

Others, like the Japanese Tendai monk Ryogen (912–985), retained the distinction between sentient and insentient beings but argued for the inclusion of plants into the former. Ryogen radically claimed that plants desire enlightenment and perform religious practices to that end. As such, they are sentient. He based his argument not only on scripture but also on observations of plant life. Sprouting, leafing, reaching, and withering looked to him like the very materialization of the path:

Plants are endowed with the four phases of life (shiten): birth, stability, alteration, and death. These are the shapes of [the four stages of spiritual life:] arising the desire [for enlightenment], religious practice, bodhi, and nirvana, as far as plants are concerned. Do plants not then also belong to the category of sentient beings?

In other words, not only do plants have a spiritual life, they are the spiritual life. They render practice botanical. Like much contemporary science, Ryogen’s approach is anthropomorphic, projecting human traits onto plants. At the same time, Ryogen acknowledges that plants exhibit these traits in a patently vegetal fashion. Plants sprout where we might join a sangha. They leaf where we put our hands in gassho. They wither and die where we might finally extinguish the grasping mind.

But why apply human concepts to plants at all? Plants perform remarkable feats that put our flesh sacks to shame. They feast on sunlight through photosynthesis. Some live for thousands of years. One imagines that if the vegetal kingdom applied its criteria to humans, we would come up short. This alterity invites us to appreciate plants on their own terms. In this vein, Chujin (1065–1138), another Tendai monk, stated:

As for trees and plants, there is no need for them to have or show the thirty-two marks (of buddhahood); in their present form—that is, by having roots, stems, branches, and leaves, each in its own way has Buddhahood.

Chujin permits plants to live enlightened lives in their own way and on their own terms. Because of this, humans can never fully understand plants from a plant’s point of view: “The self-nature of trees and plants is not capable of being described, and, therefore, the buddhanature possessed by trees and plants is also ineffable.” There is, borrowing from the thought experiment of the American philosopher Thomas Nagel, “something it is like” to be an enlightened plant. But humans, in our limited knowledge, may never apprehend it.

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Paco Calvo continues his research into plant cognition and consciousness. His lab at the Universidad de Murcia currently researches, among other topics, learning and goal-oriented behavior in plants. How do they process information, adapt to new circumstances, and make intentional decisions to achieve specific goals?

As far as I can tell, this research has not yet reignited widespread debates within Buddhist communities regarding plant sentience. The question of plant minds seems to have receded within Buddhist discourse over the past several hundred years, even as concern grows over climate change, habitat destruction, and species extinction. One may be tempted to assume that seeing plants as conscious is a necessary step toward preserving the environment. But countless Buddhists have cultivated ethics of care for the natural world that altogether sidestep the questions of whether beings like plants have minds. For example, the public leader and Thai monk Buddhadasa Bhikkhu (1906–1993) did not maintain that plants or animals were sentient yet urged Buddhists to care for the natural world as part of a process of realizing dependent origination. Influenced by Buddhadasa, Thai monks in the 1980s and 1990s tied saffron robes around trees, ordaining them to protest their destruction for the purpose of commercial logging and pipeline construction. And His Holiness the Dalai Lama himself penned an extensive ode to trees as icons of interdependence, which calls on each of us to take up more ecological responsibility.

So where should we look to settle the question of plant minds? I confess: over the past year, I have immersed myself in plant research, hoping that science would tip the scales definitively one way or the other on the existence of plant minds. But as my appreciation for this research has grown, so too has my skepticism. Echoing Chujin, I question if the physical sciences can fully account for something as ungraspable as the mind. The contemporary study of consciousness feels like a kaleidoscope, whose terms reconfigure with new evidence, resisting any definitive orientation. Even within research of human consciousness, there remains a gaping explanatory chasm between maps of neural networks and the joy I experience when my dog licks my face, or when the grief of a lost love shatters time.

It is within this chasm that I sit zazen. As a Zen practitioner, I return to personal, embodied practice as a valid and vital means of acquiring knowledge. I think of how Eihei Dogen (1200–1253), in his writings, consistently puts “body” and “mind” together in one term—shinjin, or body/mind. Our bodies house wisdom. No wonder Dogen chides us for expending too much energy on an abstract notion of mind rather than a direct experience of it: “Students . . . consider the mind to be thoughts and perceptions and do not believe it when they are told the mind is plants and trees.” For Dogen, the question is not whether some beings manifest something called mind or buddhanature. It’s not even if buddhanature manifests in all beings. Rather, buddhanature is being. It is all concrete phenomena. As he famously states, “If I were to explain the buddhanature without getting too involved, [I would say that it is] fences, walls, roof tiles, and pebbles.” We might add to that list daisies, dahlias, strangler figs, acacia.

For Dogen, all life preaches the dharma, and listening requires something beyond ordinary perception. In his Shobogenzo Mujo-seppo, Dogen quotes a poem by the Chinese monk Dongshan: 

How wondrous! How wondrous!
The expounding of the dharma by insentient beings is unthinkable.
If I tried to hear it with the ears, it would never be possible to understand.
Only when I hear the voice with my eyes am I able to know it.

I believe it is only through deep practice that we may hear the voice of plants “with our eyes.” And yet I do not believe science must be pitted against religion, nor must one contort itself to appeal to the terms of the other. Science often leads me to the door of wonder, teaching me to see new things with my eyes. But practice is what trains me to enter, leaving behind my sight.

Influenced by plant science, my Zen practice has become a hybrid form I can only describe as “lingering.” I linger—as countless Buddhists since Gautama have—at the base of a tree with grass as my cushion. I pick one being upon which to focus—most recently, a black birch. Bringing to mind plant science, I imagine the birch’s life: how it is constantly sensing the moisture and acidity of soil and detecting the strength and direction of the sun. I recall the electrochemical chatter that passes between its neighbors through the air and underfoot. In short, I try to sense how this tree is alive in each moment, despite lacking obvious outward movement.

I bow, recognizing that my life, my body/mind, is owed to vegetation. Plants first rendered Earth habitable by producing oxygen. Vegetation created the very atmosphere I live in, the breath that I am. They make matter solar by constantly converting light into sugar, which they eat, and so do I. Plants constitute a chemical interdependent co-arising.

Lingering, my body/mind becomes fluid, malleable, protean—much like a plant. Boundaries between the fleshy, vegetal, terrestrial, and the celestial dissolve. What is inside a plant? What is outside? Where is the mind?

As Suzuki Roshi said, “What we call ‘I’ is just a swinging door which moves when we inhale and when we exhale.”

Breathing, I smile. The birch does too.