Plant Cuttings

Chapter 6 – The intelligent plant(?) – is one of the shortest sections in the draft book. In a bid to rectify that deficiency this is the first of a short series of posts that will provide some examples of plants doing ‘clever’ things. Whether we actually call them clever is a personal decision. And, decision-making is what it often comes down to. But, does the ability of a plant to make decisions indicate true intelligence at work? I leave that to you to decide. But, as far as Mr Cuttings is concerned plants are pretty dam’ good at making the right calls…

[Ed. – if you think I’m using language in this post that is less than scientific and objective, but is more subjective, and may indicate intent or conscious decisions or ‘agency’ on the part of plants, I hope you can put that down to one of two things – and probably both of them. One, my lack of imagination and expertise in English word-choice; two, a demonstration of the difficulties we have in using English – and probably any other written human language – to describe the phenomena that plants exhibit when we consider how ‘intelligent’ they may be. The latter is a problem that’s at the heart of the whole debate about plant intelligence – trying to find the right words to describe the actions of a group of organisms that are not human being.]

Anyway, here’s the first example…

Maximising pollination success: colour-changing sexual parts

This image of Saxifraga fortunei, by “Bentham-Moxon Trust.; Curtis, William; Curtis’s botanical magazine dedications, 1827-1927: portraits and biographical notes; Royal Botanic Gardens, Kew; Stanley Smith Horticultural Trust” is used under the Creative Commons Attribution 2.0 Generic license.

Most – 90% (Ze-Yu Tong et al., 2023) of – flowering plants recruit the services of animals to help them create the next generation, by moving pollen from male to female parts of flowers*. Amongst this army of sexual-facilitators are butterflies (Erik Stokstad), birds, bats, bees, beetles (Jacob Muinde & Daniel Mutavi Katumo, 2024), and baboons [Ed. – but, NB, not every animal whose English name begins with a ‘B’ is necessarily a plant pollinator…].

To promote success in this phytoprocreational process, many plants display a range of colours (e.g., Eduardo Narbona et al., 2021) in a variety of floral organs (e.g., Renee Miller et al., 2011). For example, bull’s eye patternings in the tepals of the day lily (Hemerocallis sp.) (Ross E Koning), and between disc (Arieh Tal) and ray (Arieh Tal) florets (Lizzie Harper) in Rudbeckia (Ross E Koning). This variety of positioning and colour combination is often linked to plants attracting the attention of specific pollinators (e.g., here, here, and here [Ed. – but do see discussion of this topic by Beverley Glover (2009)].

However, successfully attracting the correct pollinator using the appropriate coloured plant part can be counter-productive (from the plant’s perspective) if there are repeated visits to the same flower after it has already been successfully pollinated. To avoid – or at least minimise – such wasteful encounters – several plants have hit upon the idea of changing the advertised colours to indicate that the flower has already been pollinated (Ray Cannon; Jason Chan)**, and encouraging the would-be pollinator to try another flower/plant.

Not only is this of benefit to the plant, but alerting insects to the fact that a flower has been pollinated may also prevent it having a wasted journey if part of the ‘payment’ it would usually receive for providing this pollination service is provision by the plant of nectar and/or pollen as a food reward (Nur Athirah Zariman et al., 2022; Daniel Murphy). An already-pollinated flower may not provide as much, or any, of that reward as a non-pollinated one (Steve Benham; Edward Hill).

A subtle example of pollination-associated floral colour change is described by Kazuma Takizawa et al. (2026) in Saxifraga fortunei (Saxifragaceae). In this instance, rather than large-scale changes in colour of showy floral parts such as petals, the chromatic shift takes place in the pistils, the central female parts of the flower.

In words, the pistil (Ann Marie VanDerZanden) is “the female reproductive part of a flower. The pistil, centrally located, typically consists of a swollen base, the ovary, which contains the potential seeds, or ovules; a stalk, or style, arising from the ovary; and a pollen-receptive tip, the stigma, variously shaped and often sticky” (quoted from here]). Visually, it can be seen in the image below:

Diagram of a eudicot (Douglas E Soltis & Pamela S Soltis, 2021) flower showing and naming its parts. Image borrowed with gratitude from the University of Illinois.

Noting that pistil colour often changes from yellow to red after successful pollination, what significance did Takizawa et al. (2026) attach to that observation? Knowing that hoverflies number amongst the plant’s most common visitors, and that they are often drawn to yellow but less sensitive to red, Takizawa et al. (2026) wondered whether the pistil’s colour-change was acting as a guide, attracting the insects to unpollinated flowers and discouraging them from visiting already-pollinated ones.

The overall findings of their elegant study (which is well worth reading in full), that combined work in the field (over three seasons) and microscopical examination of the flower structures in the lab, were: that pistils first appear yellow, and remain that colour until successfully pollinated when they turn red. Reinforcing the colour difference seen in visible light, red pistils strongly absorb UV whereas the yellow ones reflect it. Hoverflies (and honeybees) were observed to visit yellow-pistilled flowers, but not those with red pistils. The naturally-occurring colour change was reproduced experimentally with hand-pollination of flowers. All of which evidence points towards pollination being linked to the colour change, which is seen by the plant’s insect pollinators. The absence of pollinator visits to red-pistilled plants would strongly support the proposal that the insects are spending more time visiting plants that had not yet been pollinated.

And this phenomenon*** doesn’t appear to be unique to Saxifraga fortunei. Takizawa et al. (2026) found the same pistil colour-change in closely related plants in the Saxifragaceae (the saxifrage family of flowering plants), Saxifraga rufescens, S. serotina, S. mertensiana, and Micranthes occidentalis.

For a great analysis and interpretation of this study, see the scicomm article by Victor HD Silva.

An intelligent saxifrage..?

Is this a case of the plant being clever? Maybe. Although the more guarded amongst us are likely to posit the notion that this is merely an example of evolution that has fitted the plant to its environment. The colour change may have occurred randomly but, because it had survival benefit – enhancing the likelihood of pollination and producing the next generation, became fixed as part of the behavioural repertoire of the plant. Whatever the reason, it’s another example of the weird and wonderful in the natural world and one we should rightly celebrate – and a great example of the ‘clever’ things that plants can do.

There’s more…

And, it is important to bear in mind, that if a colour change is noticed by a human, it is likely to be much more noticeable by, and obvious to, the animal to which it acts as a signal. Why? Because non-human animals often have different visual sensitivities to people. For example, (many) insects have the ability to see UV wavelengths [we cannot], which gives them a quite different view of the colours and visual patterns/colour-guides that surround them (as noted in Takizawa et al., 2026‘s saxifrage study). Which means there may be many more examples of ever-so-subtle wavelength/colour shifts in nature that we humans are completely oblivious to.

And that’s just one more example of events in the natural world that may pass us by if we don’t look in the right places, at the right time, with the right equipment/techniques, and with the right – open – frame of mind…

* Always keen to maintain balance, we are happy to advise that not all plants use biological lifeforms (overwhelmingly animals) to assist their sexual aspirations. Whereas living creatures are technically described as biotic factors (Mark Dziak, 2024), about 10% of flowering plants aren’t animal-pollinated (Ze-Yu Tong et al., 2023, and its press release here). Instead, those plants rely on so-called abiotic factors (Autumn Spanne, 2024).

Amongst the most common abiotic factors are air currents – wind if you like – as in the distribution of pollen in oak and maple, and crops such as the cereals wheat, rice, barley, and maize. Wind-pollination [although, it is actually the pollen that does the pollination…] is technically known as anemophily.

Another – much, much smaller (C Thomas Philbrick, 1991) – group of plants engage in hydrophily (Paul Alan Cox, 1988), “a fairly uncommon form of pollination whereby pollen is distributed by the flow of waters, particularly in rivers and streams” (quoted from here). In this instance water transfers pollen from male to female parts.

[Ed. – NB, despite their watery habitat, not all aquatic plants are hydrophilous, a high proportion are actually anemophilous (Christopher Cook, 1988)].

Whilst the emphasis in this foot-note has been on angiosperms, it should be noted that many (all..?) gymnosperms also employ anemophily, e.g., pine trees (Aliaa Aly). [Ed. – and, which plants also use wind for dispersal of their seeds. Somewhat bafflingly, this behaviour is called anemophily by the American Conifer Society; the more usual technical term for this phenomenon is anemochory…].

** Educators of students aged 16-19 years interested in “Investigating How Plants Use Colour to Attract Pollinators” might like to consider the resource of that name provided by SAPS [Science and Plants for Schools], which is available here.

*** Takizawa et al. (2026) have named this phenomenon the ‘traffic-light’ idea (but this term is only found in the article’s title). Although the allusion doesn’t work that well – in the UK at least both red and yellow (amber) shown separately in traffic lights essentially mean ‘stop’ (Aaron; Barney Cotton) – it is imaginative, arresting, and memorable. [Ed. – and, maybe, for the intended pollinators, visible yellow is their equivalent of ‘traffic light green’..?]

REFERENCES

Christopher DK Cook, 1988. Wind pollination in aquatic angiosperms. Annals of the Missouri Botanical Garden 75(3): 768-777; https://doi.org/10.2307/2399365

Paul Alan Cox, 1988. Hydrophilous pollination. Annual Review of Ecology and Systematics 19: 261-279; https://www.jstor.org/stable/2097155

Beverley Glover, 2009. The diversity of flower colour: How and why? International Journal of Design & Nature and Ecodynamics 4(3): 211 – 218; doi: 10.2495/DNE-V4-N3-211-218

Renee Miller et al., 2011. Plants and colour: Flowers and pollination. Optics & Laser Technology 43(2): 282-294; https://doi.org/10.1016/j.optlastec.2008.12.018

Jacob Muinde & Daniel Mutavi Katumo, 2024. Beyond bees and butterflies: The role of beetles in pollination system. Journal for Nature Conservation 77: 126523; https://doi.org/10.1016/j.jnc.2023.126523

Eduardo Narbona et al., 2021. Major flower pigments originate different colour signals to pollinators. Front. Ecol. Evol. 9: 743850; doi: 10.3389/fevo.2021.743850

C Thomas Philbrick, 1991. Hydrophily: Phylogenetic and evolutionary considerations. Rhodora 93(873): 36-50; https://www.jstor.org/stable/23312754

Kazuma Takizawa et al., 2026. The pistil as a traffic light: Yellow-to-red color change likely influences pollinator visitation patterns in Saxifraga fortunei (Saxifragaceae). Plants, People, Planet 1–11; https://doi.org/10.1002/ppp3.70193

Ze-Yu Tong et al., 2023. New calculations indicate that 90% of flowering plant species are animal-pollinated. National Science Review 10(10): nwad219; https://doi.org/10.1093/nsr/nwad219

Nur Athirah Zariman et al., 2022. Plant attractants and rewards for pollinators: Their significant to successful crop pollination. International Journal of Life Sciences and Biotechnology 5(2): 270-293; https://doi.org/10.38001/ijlsb.1069254