Imagine if the world was invaded by aliens who were of equal intelligence to us, but just did things incredibly faster. Thanks to vastly different technology and adaptations to those of humans, these aliens were able to move faster, reproduce faster, and communicate faster. So fast, in fact, that we couldn’t perceive these things actually happening, but we could only see – and had to deal with – the results. It’s likely that the new aliens would consider us extremely primitive and stupid (even though we were not) because we simply did things differently, and at a vastly slower speed.

Stefano Mancuso and Alessandra Viola, the authors of Brilliant Green, use this scenario to get us thinking from the plant’s point of view. For many centuries, Western culture has regarded plants as second rate, primitive, beings. And the main reason for this is that plants are perceived as being inanimate – not moving. (Many people who are enthusiastic about animals can also be indifferent to plants. If asked why, they often say ‘Plants don’t move’, which has always struck me as rather lame – if you’ll pardon the pun.) Most plants certainly have a sessile (fixed in one place) lifestyle, at least for their adult phase. This has influenced how they have evolved to cope with whatever life throws at them. But contrary to popular opinion, plants do move, and in a multitude of ways. They just move a whole lot slower than many animals.

Brilliant Green argues that plants are also much more intelligent than people give them credit for. Perhaps they are as intelligent as you and I, but in a different way. I’m yet to be convinced of this last point, although I have no doubt some plants are probably smarter than a few people I could name. But the concept of intelligence is certainly worth exploring, including the various ways that intelligence can be displayed and measured. Brilliant Green takes the reader on a lively and thought-provoking journey by examining these questions from the plant point of view.

Plant leaves and shoots move towards the light, and plant roots move towards nutrients and water, and around obstacles. Plants have devised many ingenious ways to move their pollen from flower to flower, and often from plant to plant, and to move their seeds from the parent plant to where they have a good chance of germination and growth. But did you also know that plants display all of the 5 senses that humans have (sight, touch, taste, smell and hearing)? And apparently they have a whopping 15 extra senses that we do not. They can measure humidity, sense gravity and electromagnetic fields, and measure numerous chemical gradients in the air or in the ground. But the book doesn’t explain how these extra plant senses add up to 15, which is unsatisfying. (And I’d also argue that most animals have a pretty good sense of gravity.)

The examples of how plants use chemicals to communicate with animals are fascinating, especially when animal buddies are summoned to deal with other animals who are eating the plant. And comparisons between plants and other decentralised ‘networks’ of intelligence are intriguing.

One reason that plants have been viewed as primitive is that they don’t appear to have a brain or other discrete organs like animals. Yet, since plants are fixed in place, they are constantly at risk of being eaten or damaged. Having a centralised brain or stomach or heart would mean that damage / removal of these organs would result in the death of the whole plant. Instead, the plant body is modular, and the functions of sensing, circulation, absorption of nutrients, etc., are split up among numerous cells. Damage to a shoot or root will not threaten the survival of the whole plant. So plants are doing many of the same things that animals do, but in a fundamentally different way.

Even though I’d really like to think of plants as intelligent, I’m not convinced just yet. But Brilliant Green is certainly worth reading – it’s not very long, and is written in an easy and engaging style. If not entirely convincing, it certainly allows us a tantalising glimpse into some verdant possibilities in the emerging and controversial field of plant intelligence.

It’s worth remembering that Charles Darwin considered plants to be the most extraordinary living things he had ever encountered. And he had a few other useful insights that took a while to be accepted.

Brilliant Green by Stefano Mancuso and Alessandra Viola.