Sir David Attenborough on "hypnotic appeal" of nature docs like The Green Planet

“No, I can do a bit more,” he insists, turning down the offer of rowing support from Gunton, who’s now emerged from beneath the tarpaulin. And on Attenborough rows.

“When David was at Cambridge he was a rugby player and when I was at Cambridge many years later I was a rower,” explains Gunton. “He said, ‘We rugby players always thought we could row better than you rowers’ so this was him proving that we ‘wet bobs’ – as he calls us – weren’t as good at rowing as the rugby players. That is classic David.”

This new series, The Green Planet, is also “classic David”. A largely unseen vocal guide to many of the most recent landmark natural history programmes, Attenborough is back on location for this stunning and thought-provoking deep dive into the world of plants.

The filming schedule has taken him around the world – almost certainly the last time he’ll travel to so many far-flung places for one series. We see him in the freezing high Arctic, in the baking deserts of America, on a gondola high up in the tree canopy of Costa Rica and, closer to home, in Kew Gardens, the place, probably more than any other, where he feels most comfortable and where we catch up with him.

Attenborough’s been here, as he was yesterday and the day before, since 6:30am. This morning he’s observing the awakening of the humble daisy. Thermal cameras show how the warming rays of the sun prompt the daisy to emerge from its petal-perfect slumber and invite the attention of pollinators. It’s simple, but beguiling stuff.

Next, Attenborough is invited to perch on the exposed root of a 150-year-old oak tree. He remains awkwardly seated (on the face of it very patiently) for upwards of an hour delivering a few lines of dialogue while cradling a cross section of oak from another tree that, like him (it’s all in the planning), is 95 years old.

Those of us observing from 50m away are stretching arms and legs in solidarity. His daughter Susan stands discreetly in the background with the offer of a warmer coat, but Attenborough ploughs on through script tweaks and multiple takes until everyone is happy with the final version.

Why does he still do it? As ever, it’s the seductive appeal of having a gripping new story to tell, and new camera technology to tell it with.

“That is what brings the thing to life and should make people say, ‘Good Lord, these extraordinary organisms are just like us.’ In the sense that they live and die, that they fight, that they have to learn to reproduce… but just that they do them so slowly, so we’ve never seen that before. And that has a hypnotic appeal.”

The challenge for Attenborough and the rest of the Green Planet team, as it was 27 years ago for its forerunner The Private Life of Plants, has been to make the plant world every bit as intriguing, as precarious – even as brutal – as the animal world. With that in mind, they’ve even managed a nod towards that BAFTA-winning hands-over-the-eyes scene from Planet Earth II featuring the writhing mass of racer snakes.

Immersive camera technology and painstakingly assembled time-lapse photography bring this alien world to life like never before. One cactus in the US had seven cameras trained on it continuously for three years, the longest ever time-lapse study undertaken by the BBC.

For Attenborough, such star billing is long overdue. “The world has suddenly become plant-conscious. There’s an awareness that we would starve without plants, we wouldn’t be able to breathe without plants. And yet people’s understanding about plants, except in a very kind of narrow way, has not kept up with that. I think this will bring it home.”

What it also promises to bring home is a new understanding of plants that’s not just spectacularly intriguing, but also philosophically challenging. For in revealing just how sophisticated plant communication actually is, it prompts the question of whether plants possess some form of that very human quality, intelligence. And if it isn’t intelligence (after all, plants don’t have brains), then what is it?

Series producer Rupert Barrington believes our vocabulary hasn’t kept pace with our understanding of the plant world. “In some ways our language isn’t adequate – we struggle to know what to call this thing, which isn’t intelligence as we understand it, but something that’s a lot more sophisticated than previously thought.”

The standout sequence of the opening episode observes how a voracious underground fungus “employs” (the word used in the narration) thousands of leaf-cutter ants to bring it foliage food. But when the tree under attack responds, by releasing toxins to protect itself, the insects recognise the threat these poisoned leaves pose to the fungus and so switch their attention to another tree.

Such interconnected levels of communication seem barely plausible, but Barrington says we’re only beginning to scratch the surface of the underground “wood wide web”, as it’s known in scientific circles. For instance?

“Well, certain species of fungi will plug into the roots of certain species of tree. The trees create sugars by photosynthesis that they feed to the fungi, the fungi get nutrients out of the soil that they feed to the tree.” So far, so believable. But delving deeper, we begin to inhabit a world popularised by the likes of John Wyndham.

Says Barrington: “The trees also send signals down these cables very deliberately to each other and they’ll feed food down through those cables to their own offspring [saplings] – effectively caring for their young. Those trees are known as mother trees.”

And if further proof were needed of the complex botanical chemistry that underpins plant life, there’s this from Barrington. “If a tree that’s connected into this network is dying – in some way it knows it’s dying – then it sends all its stored nutrients out to its own offspring, but also to other trees in the forest.”

Barrington acknowledges that much of this new science is “mind-blowing”. “I think people are beginning to rethink the capabilities of plants,” he says, with some understatement.

Attenborough observes one such example of those capabilities for himself at Kew Gardens. He uses a paintbrush to entice a Venus fly trap into believing an insect has ventured into its jaws. But the plant recognises that a single such encounter could be anything and doesn’t respond. It’s only when Attenborough repeats the trick a few seconds later that the plant concludes it must be a moving insect and snaps shut. Proving, it’s said, that this particular plant can count.

“This is a parallel world which exists alongside us and which is the basis for our own lives and to which we have paid scant attention over the years,” is how Attenborough summarises it.

Such life-giving significance was crystallised for Barrington in a sequence – his favourite of the series – filmed on a tributary of the Amazon.

“We’d been told about plants that hyper-produce oxygen when the sun comes up. It’s this wall of bubbles of pure oxygen – utterly beautiful, like a river of champagne. You look at it and think, ‘This is profound’, because that plant is creating the atmosphere – you can actually see it producing the oxygen we need.”

Attenborough embraces that sentiment. “Over half the population of the world, according to the United Nations, is urbanised, lives in cities, only sees cultivated plants and never sees a wild community of plants. But that wild community is there and we depend upon it. And we better jolly well care for it.”

The Green Planet starts 9th January on BBC One at 7pm. To find out what’s on TV tonight, check out our TV Guide or visit our Documentaries hub for all the latest news.

This feature originally appeared in the Radio Times magazine. For the biggest interviews and the best TV listings subscribe to Radio Times now and never miss a copy.