Intelligent Plants?

A Sensitive Plant in a garden grew,
And the young winds fed it with silver dew,
And it opened its fan-like leaves to the light.
And closed them beneath the kisses of Night.

The Sensitive Plant, a watercolour by Frank Bernard Dicksee (1853-1928) depicting Percy Bysshe Shelley’s poem (see above). Public domain, via Wikimedia Commons.

The publication of a recent paper (Khattar et al., 2022) [1] examining acceptance among scientists of various disciplines of the concept of plant intelligence provoked online enthusiasm among some herbalists, in terms such as:

“It hearkens to an emerging, emboldened approach to scientific investigation that finally dispenses with monotheism-informed, limiting belief structures and subtexts, allowing for the contemplation of intelligence and consciousness in non-human beings… (such as) …plants and dissimilar creatures in particular.”

The paper’s authors acknowledge that semantics is an issue and provide the following definition of plant intelligence:

Any type of intentional and flexible behavior that is beneficial and enables the organism to achieve its goal.”

They give some examples of behaviours which might be viewed as evidence of plant intelligence:

“the ability to problem-solve in a flexible manner, anticipate the future, store memory, learn, communicate, and ultimately be goal-oriented.”

Specific examples include:

  • Volatile chemicals being produced at the appropriate time, concentration, and amount as defence against herbivores.
  • The above behavioral responses affecting, and being affected by, neighboring plants, shaping plant communities.
  • The capability to custom-modify the quality and quantity of their nectar to attract the right species of ants to protect them, a capability that requires plants to sense the presence of different ants, and to monitor and modify their own activity accordingly.
  • The ability to anticipate the future as demonstrated, for example, in the way plants rely on light cues to remember the exact number of warm days or daylight hours (i.e., photoperiodic control) that have passed to develop their leaves and flower.
  • The ability to learn to make new associations through multiple cues and to respond adaptively. Conditioned learning of this type has been demonstrated in the pea plant (Pisum sativum L.).
  • Various types of foraging behavior for sunlight and nutrients exemplify how plants can be goal-oriented. Example: the ability of the pea plant to modify root-growth in response to varying nutrient concentrations.
  • The capability to manipulate herbivores to adopt cannabalistic behaviour by releasing certain chemicals, as demonstrated by some tomato plants (Solanum lycopersicum L.).

These capabilities are indeed fascinating, but do they demonstrate intelligence? This clearly hinges upon our definition of intelligence, and according to the study author’s definition, I would judge that they do not. The problem is with the word “intentional”. I would agree that to be “goal-oriented” is not enough for a behaviour to demonstrate intelligence, it must be intentional. And does not intention imply consciousness? None of the behaviours described above demonstrates consciousness. It may be there at some level (if not individual then within the community), but it has not been shown to be there.

But I am more interested in a further facet of this debate. Just say that we all agreed that plants possess some form of intelligent consciousness (remember, intention requires consciousness), would that be be anything like ours, something we as human beings could relate to? Because this is what some herbalists fancy. That plants can talk to us and we can understand them; even that they may feel well-disposed towards us.

I have little doubt it would not. I know quite a lot at an experiential level about fish, which are more closely related to us than are plants. I swim with them often and sometimes I catch them to eat. Some species are curious about people, most are not, and some will swim away very fast at the first sight of a human being. I like them. But they cannot “like” me, even the curious ones, they are merely curious in some kind of fishy way. Why on Earth should intelligent fish like human beings? If I were an intelligent fish I would have a great big prejudice against them, wouldn’t you? But fish are most probably incapable of emotion. Their behaviour is goal-oriented (even intentional) and flexible, but whatever form their “thoughts” take, they are nothing like mine. I can hardly conceive of what it is like to think like a fish. Tell me, what part of the above reasoning cannot be applied to plants?

For some herbalists there is the romantic temptation to anthropomorphise plants or to project their own thoughts and feelings onto them, but beware! Subjective realities, while valid in some terms and for some purposes, often boil down to simple flights of fancy.

[1] Khattar, J., Calvo, P., Vandebroek, I. et al. Understanding interdisciplinary perspectives of plant intelligence: Is it a matter of science, language, or subjectivity?. J Ethnobiology Ethnomedicine 18, 41 (2022).

One Man’s Understanding of Vitalism in Herbal Medicine

Photo “Elemental” by the author


For the purposes of this article vitalism is that attitude that focuses on the quality and characteristics of vitality in the organism. Vitality is the potential for life and health. Only vitality heals.

The great ancient civilisations developed elemental-energetic models of existence that encompassed the cosmos, living beings, physiology, health, disease and medicines. The Chinese had and still have a five-element system, Ayurvedic medicine had and still has its five elements and three doshas, and Greek-Unani medicine had its four elements and four qualities. All these systems had several things in common, but above all it was their focus on vitality that characterised them and differentiated them from modern medicine.

The Greek system has remained in modified form in modern Western herbalism, referred to as “energetics”. Some practitioners refer to this system, others do not. I have never taken to this usage of the word “energetics”. In my view it is important to realise that the usage of terms such as energy / energetics / hot / heat / warming / heating / cold / cooling / dry / drying / damp / moist / moistening is often (not always) metaphorical rather than literal. They are rules of thumb, heuristics, and should not be made into dogmas. Contradictions, incongruences, and paradoxes are part and parcel of such heuristics, and frustrating misunderstandings come from taking this thing too literally. Heat, cold, moist, damp, wind do not exist as energies, they are labels for mind associations that we make. They are man-made, not nature-made! These are not energetic systems but symbolic systems.

Secondly, the kinds of interactions taking place when medicinal plant material entering the human body affects human physiology is more often than not informational rather than energetic.

Another point about the neo-classical so-called “energetic”system of some modern Western herbalism is that while it considers qualities (such as hot, cold, dry, moist) it almost completely overlooks something fundamental which really is energetic: the global energetic potential (potential for vitality) of the person, “energy level” for short.

Towards a Better Vitalistic Understanding

First of all let me say that I am claiming nothing new or original in anything that follows. I have written this for myself, for the sole purpose of clarifying a few things in my own mind.

Let me formulate four working principles:

  1. Physiological energy is transformed in three major ways, as heat, movement or mass.
  2. All ill-health begins with hyperfunction or hypofunction, whether you call it warming, cooling, drying, moistening, contracting, relaxing or whatever.
  3. Energy level (vital potential) heavily influences how hyperfunction and hypofunction express (i.e. nature of symptoms, pathology)
  4. Chances are you are greatly under-estimating the influence of the mind!

Heat, Movement and Mass

It seems to me that of the old-world models, the Ayurvedic three-dosha construct approximates most a proper energetic model, inasmuchas the three doshas of Pitta, Vata and Kapha partially reflect the three major expressions of physiological energy: heat, movement and mass respectively.

Heat: The production and maintenance of body heat or anything that promotes or facilitates this. I am thinking of thyroid hormone activity and a good supply of substrates for it, implying efficient metabolism and digestion. Heat must also escape, if there is not to be over-heating. There is a hot-cold continuum (or dimension). Perspiration is our natural cooling system, so this is considered along with heat on a hot-cold axis.

But we needn’t be too literal about this and thousands of years of collective experience and reflection suggest that a little figurative thinking adds rather than detracts from the effectiveness of the model. So things that feel hot, are conflated with the idea ‘heat’: things such as any kind of acute inflammation, burning pain like heartburn from gastro-oesophageal reflux, a burning sensation on urination due to infection or inflammation, or the burning quality of some neuropathic pain. And things which feel worse with heat (acute inflammation, some headaches, and so on) we shall also call ‘hot’.

The opposite of too hot is obviously too cold, and a normal physiological balance is found in the middle. As with heat, cold is either something which allows us to become cold (deficient heat generation) or something which feels cold or gets worse with cold.

Movement: Voluntary muscular activity as well as smooth muscle, cardiac, secretomotor and involuntary skeletal muscle activity (e.g. shivering). We can already begin to see that there is (inevitably) interaction between our basic categories of physiological energy transformation. Heat is a bi-product of movement, and heat produces movement. The opposite of movement is stillness, which can come about through lack of neuromuscular activity or excessive neuromuscular activity (spasm). (Here only the variant of energy levelcan provide a coherent theoretical differentiator between the two. In practice, it is easy to do: the one is soft/lax and the other hard/taut). Health lies in the middle.

Mass: Anabolic activity both normal (muscle building, fat deposition) and abnormal (e.g. tumours). I am thinking too of passive processes or processes of omission such as oedema (this being the result of a deficit in the “movement” department). We also include things that feel heavy, such has ‘heavy legs’ (e.g. fluid stagnation due to venous insufficiency), or a heavy feeling in the lower abdomen (e.g. associated with dysmenorrhoea or prolapse). The opposite of weight gain or mass increase is weight loss, atrophy or wasting. Again, health lies in the middle

The Amoeba

I think of this trinity of heat, movement and mass as forming three contractile and projectile limbs supporting an ameboide shape called vitality. This form can change shape in a fluid sort of way, with shifts of its centre of gravity in any direction in three dimensional space, the dimensions of which being these three variables. Normal vitality is delimited within this space. If the amoeba extends in any direction beyond these limits for any length of time, ill health will ensue. Ill health can then be understood as increases or decreases of energy transformation. The latter can be categorised literally or figuratively as changes in “heat”, “movement” and “mass”. From now on to signal when these are not always literal categories I will capitalise them: Heat, Movement, Mass.


All of the herbs we use can be used on the bases of this scheme in an allopathic way, but a holistic, vitalistic allopathic way. Allopathic because we use opposites to effect a return to balance. Holistic, because we consider the whole organism. Vitalistic, because we are primarily concerned with the organism’s vital potential.

Cooling herbs are anti-inflammatory, antipyretic, demulcent, diaphoretic, peripheral vasodilators (cooling to the centre), tonic or mimetic to the parasympathetic nervous system, or subjectively cool like bitters.

Warming herbs are antirheumatics, aphrodisiacs, aromatic digestives, circulatory stimulants, metabolic stimulants, peripheral vasodilators (warming to the periphery) and rubefacients.

Peripheral circulatory stimulants and diaphoretics (many herbs are both) are a bit of a paradox. They take heat from the core out to the periphery, where is is dispersed by diaphoresis. They make you feel warm to begin with but they are actually cooling you down. The lesson is to use them cautiously and sparingly unless we are sure of efficient digestion and metabolism. Happily, many are also digestives!

Movers: Aphrodisiacs, cholagogues, circulatory stimulants, deobstruents, emetics, emmenagogues, expectorants, galactagogues, glandulars, lymphatics, mood enhancing nervines, stimulant laxatives, stimulating tonics, vasotonics, sympathetics or parasympathetics depending on which system we are considering.

Calmers and stoppers: Analgesics, anxiolytics, antispasmodics, calming nervines, carminatives, haemostatics, hypotensives, relaxants, sedatives, soporifics, sympatheticolytics.

Builders and strengtheners: Tonic nervines, nutritives, appetite-stimulants, immune stimulants, restoratives, restorative tonics, trophorestoratives, vulneraries.

Trimmers, cleaners, and softeners: Antitumorals, astringents, bulk laxatives, catabolic stimulants, cholagogues, depuratives, detumescents, diuretics, emollients, hypoglycaemics, hypo-uricaemics, mucolytics.

Hyper- and hypofunction

I am in accord with certain authors of the Physiomedicalist and Eclectic movements when I say all illness begins with an increase or decrease in a physiological function. They used other terms: Heat/Cold, Excitation/Relaxation. I use hyper- and hypofunction. The idea is the same – imbalance along a physiological spectrum – but it is broader, a higher level definition.

Hyperfunction and hypofunction can affect the tendencies towards Heat, Movement or Mass. By and large (not always) these are active processes requiring energy expenditure, whereas their opposites are generally (not always) passive. Warming up is active, cooling down is passive (vasodilatation is smooth muscle relaxation). Movement is by definition active, inaction is passive. Mass is a bit more ambiguous. For instance energy is expended both to build up and to break down adipose, however overall there is a net gain in energy in the longer term economy of the organism, energy that may then be utilised by the body for activity, body heat production, or body maintenance activities. Fluid stagnation (Mass) is a passive process, while its dispersal (Movement) requires energy.


Harmonisers are that class of herbs which tend by their particular chemical composition, to bring balance to one or more of these dimensions, whether the initial state is hyper- or hypo-. An example is Hawthorn, which tends to normalise high or low blood pressure. Sometimes these plants are called “tonics”, sometimes “alteratives”, sometimes “adaptogens”; they may do all these things at once, they are only labels!

Energy level

This is the forgotten variable in herbal medicine! But one of vital importance. Different people have different levels of what I will call vitality, a composite of potential for physical energy transformation, enthusiasm, hardiness and resilience.

One’s energy level influences how symptoms of hyper- or hypofunction manifest. For example, to speak in general terms hyperfunction will lead to depletion of resources and exhaustion in the low energy subject, but plethora (diseases of excess) in the high energy one. Hypofunction will lead to lethargy in both low and high energy subjects, but while in the former this will be characterised more by extreme fatigue, in the latter it will mean accumulation and deposition: lymphatic congestion, oedema, obesity, atherosclerosis, diabetes.

The hyper-/hypofunction continuum can be thought of as one of rate and excitability, while the “energy” continuum is one of stiffness/laxness. Health is balance in the interplay of these factors.

What makes the effect?

“The effect of medicinal plants is due to the chemicals contained in them, called active principles.”

This is the first sentence of a recently published literature review detailing the phytochemistry of some commonly used medicinal plants in Romania1.

Posing this as a philosophical proposition on an internet forum, I asked for people’s comments. One person asked an astute question: “Is chemistry a part of energetics?”

I am not among those who believe in subtle, vital energies, disembodied from the chemistry of life. I do not believe, for example (an example that has been expressed to me), that the interaction of a plant medicine with the person who takes it is influenced by the emotions of the grower or harvester of the plant. I believe, on a physical level, that chemistry is the most important, basic thing; and beyond that physics. And beyond physics we do not know, although we guess and make believe.

But there are some for whom so powerful is their wishful thinking that they perceive truths in their fantasies, and then make dogmas out of them, and this blinds them to the true awesomeness of the chemistry of life. Or, they think that since it is complex and mechanistic, therefore it is boring; they have no time for that, they have something better, more magical, called intuition, they kid themselves. Not that I think ill of intuition, it is just that one needs to be extremely self-aware to separate true intuition from make-believe, and people with such reliable self-awareness are in a small minority.

To me, on an equal level of importance as the physical is that of the psyche, and that too is truly awesome. Some will say this is Cartesian thinking, to speak of the physical and the psychological being “on the same level” as if considered as two things, but these people who say this paradoxically are only able to think in black and white! Things can be different but at the same time the same at a different level of thought. Otherwise all thoughts and words are futile.

The psychosocial aspect of the relationship between giver and given-to, and the attitudes and beliefs of the given-to are real game-changers, aspects almost wilfully ignored by many in the field of alternative/complementary medicine. What is my guesstimate of the influence of non-specific effects in the overall effectiveness of a plant medicine? Anywhere from 0 to 100% depending on all the variables that go on in real clinical practice. What is my guesstimate of the influence of so-called “subtle energies”? 0-5%. This allows for the possibility that I’m wrong about their non-existence, but even if that were so, by my guesstimation the aforementioned contextual and psycho-social effects would far outweigh the importance of nebulous “subtle energies”.

So, with the above proviso about psychology, I would broadly agree with the statement at the head of this section: chemistry is the mechanism by which an individual plant sample exerts a physiological effect. But organic chemistry, biochemistry, phytochemistry, phytopharmacology, human biology are frighteningly, awe-inspiringly complex. So we make our folk models which are practical and useful attempts to make sense out of a complexity we can by no means fully understand, indeed which are by no means fully understood, but which we are obliged to navigate. One of these is the tridosha model of Ayurveda, the model which I have found most useful of all and from which I have taken inspiration to develop in my own mind the Heat-Movement-Mass construct and the four principles outlined in the aforethe titlegoing paragraphs.

1 Paciana I, Butnariu M (2021) Highlighting the Compounds with Pharmacological Activity from Some Medicinal Plants from the Area of Romania. Med Aromat Plants (Los Angeles) 10: 370.

Copyright © Robert Hale 2021.