Tree of diplomacy

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1:22May 2026. Inside the garden within a garden of China's elite party estate, Zhongnanhai, President Xi and President Trump are wrapping up a state visit between the two most powerful nations on earth.

1:40The walled-off imperial garden compound, known as the Jinggu, is rarely open to foreign visitors. Lian Libai, intertwining Cyprus, have weathered the politics here for nearly 300 years. Roots stretch up, wrapping the two trunks together and binding them. Centuries-old trees, so wide that five people linked together can't touch hands around their trunks. How can I do so cool? Take a look at the tree.

2:17Two trees. It's a hundred years ago. The history of about 100 years. It's not just 100 years ago. 200. Goes to 200. President Xi gestures to the Lian Li Bai, pulling his fingers up towards one another to symbolise their coming together as he walks with President Trump. I tell you, this tree is all 200-300 years ago. There's 400 years ago. All the trees here are around 200 to 300 years old. And the big one, just behind it, 400 years old. They lived a lot in this tree. This is not so long. Yes, there are 1 ,000 years old. And there are trees 1 ,000 years old. Nice, nice place. Nice place. I like it.

3:05I like it. I like it. We stayed to look at some of the old trees. The president was interested to learn all about that, including the Chinese roses, which he looked at. And I agreed to send the seeds for these roses to the president as he gives. I love that. That's great. Thank you, honey. What may seem like a simple photo op goes far deeper than that. These trees embody a soft power that's been kept alive between the two most powerful countries on Earth for decades. Botanical diplomacy. I wake up every day and my focal point is plants. My colleagues across China, we wake up thinking the same things.

3:53We're just curious and curiosity just transcends everything. Welcome to the documentary from the BBC World Service. This is The Tree of Diplomacy. I'm Finn Aberdeen. As a journalist and as a producer, I've focused on China for two decades. And this is the story of boots-on-the-ground botany that's kept China and the US talking for over 100 years. The first science to reignite communication and help renew ties after the Cold War. And a collaboration that's borne political fruit in the form of trade deals, agricultural innovations and even shared policy aims for tackling climate change. From the outside, relations between the two countries have been anything but straightforward.

4:48China and the US are spiralling deeper into a trade war. Disagreement could even lead to conflict. US tariffs against China add up to 145%.

5:01Finn Aberdein:China has condemned the US blockade. China has a scheme to steal state secrets from the West.

5:14Another one. Do you see the bucket? There, yeah, there. A lot of it's very common. Far from conventional politics, in ancient forests like this one in China's Shenlongjia and the woodlands of the Appalachia in the US, a special kind of dialogue has taken root. It's a yellow flower. Right here. Oh, yeah. The flowers are giant. They're big, so that's the problem. That one in this tree here? Yeah, yeah. I don't care. I see a couple of those. Groups like NACPEC, that's the North America-China Plant Exploration Consortium, are practicing something deceptively powerful. It's a scientific language and a form of soft power known as botanical diplomacy.

6:13In fact, botany is the perfect example of that invisible college that has operated really below the political radar for centuries. Dr. Caroline Wagner is an academic, policy analyst and one of the world's leading scholars on international scientific collaboration. It's a very long tradition and it is a bit unique because it's a field science like archaeology or glaciology where you actually have to go there in order to advance the science. It's a relationship that is far older than any of the headlines. The story of what would become knackpeck really began at the turn of the 20th century, with the quest for the legendary dove tree, an elusive species shrouded in Chinese folklore, otherwise known as the ghost tree.

7:11At the turn of the 20th century, imperial China was in a state of terminal decline, as thousands of years of dynastic rule were drawing to a violent close. At the same time, aggressive Western expansion and economic hardships provoked the Boxer Rebellion in 1899, an anti-foreign, anti-imperialist uprising. Several thousand foreign troops, including Americans, marched on Beijing in response. In that same year of 1899, a young Englishman arrives in China. His name is Ernest Henry Wilson. He's 23 years old, he's newly engaged and he's been sent by a London plant nursery with a single precise instruction, to find the dove tree.

8:02Finn Aberdein:Wilson is another name called a Chinese Wilson. Dr Wang Kang is one of China's preeminent botanists. From his base at the Beijing Botanical Garden, he's been working with NACPEC since 2001. First as a young intern and now as one of the key Chinese coordinators for joint expeditions. He's seen the collaboration from both sides of the Pacific. When he was very young, he worked for Birmingham Botanical Garden and a cube. In 1899, the Vichy Company tried to find a dove tree, the Vedia. So that's the reason the young boy, 23 years old, before his marriage, he first time came to China. It's very difficult for him.

8:54Finn Aberdein:He had to take a long trip to China to travel from UK to Hong Kong and take the ship to Vietnam. And from Vietnam, he traveled about half a year. But unfortunately, when he followed the information to find the tree, the tree was cut by the local people. So he was very disappointed about this. But he's lucky. A couple of months later, he found another tree and got enough fruits, means seeds, and shipped back.

9:32Well, right this moment, we are on top of Bussey Hill in the middle of the Arnold Arboretum. Michael Dostman, keeper of the living collections at Harvard University's Arnold Arboretum. He's an Indiana Jones-esque plant explorer, leading on NACPEC missions from the U.S. side of the relationship. We are in a very special garden area known as the Explorer's Garden. Right now, my hands are resting on a dove tree, a Davidia involucrada. It's just a gorgeous sight to behold. The tree Michael Dostman is touching is descended directly from seeds Wilson brought back from China over 120 years ago. On May 19th, when collecting near the hamlet of Tawan, distant some five days southwest of Ichiang, I suddenly happened upon a Davidia tree in full flower.

10:26It was about 50 feet tall, an outlying pyramidal, and with its wealth of blossoms was more beautiful than words can portray. The distinctive beauty of the Davidia is in its flowers. They are pendulous on fairly long stalks, and when stirred by the slightest breeze, they resemble huge butterflies or small doves hovering amongst the trees. Wilson would make five expeditions to China in total. When he joined the Arnold Arboretum, he became keeper of the living collections, the title Michael now holds himself. It's an honor to bear the same job description, but Wilson could never be repeated. He's just an incredible botanist and horticulturist and photographer.

11:10And so if I could be one percent of what he was, that would be an honor.

11:14Finn Aberdein:I think I know more about Ernest Wilson than the common English people. He introduced about 1 ,000, maybe more than 1 ,000 species to the horticulture market to enrich the species in the garden, especially in European gardens. I think he's the number one in the world to do the seeds collecting or exploration for plants. Most of us should thanks him for his legacy. Wilson's early expeditions to China established a botanical relationship between East and West that endured to the present day. But he wasn't working in isolation. Even as he explored, Chinese botanists were developing their own ties across the Pacific.

12:07One of the most significant was Hu Xian Su. born in 1894, who received his doctorate from Harvard and trained in part at the Arnold Arboretum itself. He went home and became a founding figure of modern Chinese botany. And in the 1940s, he did something that would echo through botanical history for the next 80 years. The only thing we knew about the Don Redwood was that it was extinct. Ned Friedman is the current director of the Arnold Arboretum. We thought all we have is a record in the rocks, fossils that are millions of years old. And then word starts to leak out from this very small remote part of Hubei that perhaps the thing that we thought was extinct is actually alive and well, truly a living fossil.

13:01Ned's alluding to the giant dawn redwood, a tree then thought to be long extinct. It was like discovering a dinosaur that still walks the earth. One of our alums, Hu Shinsu, who actually 100 years ago received his doctorate from Harvard University, from the Arnold Arboretum in botany, he was one of the founding botanists in China. Michael Dosman. He made the link that this plant found as a fossil and given a name was actually living and breathing there in central China. So it was a celebration of botany across east and west. Those seeds were collected in the fall of 1947. So the thing that makes this tree so sort of emotionally resonant is to think that all you could know of this tree was by opening, cracking open a rock.

13:53And now you get to see it alive. And it still sends chills down my spine to be standing next to this wonderful tree. The Dawn Redwood seeds arrived in Boston in January 1948, while civil war was still raging in China. The tree Ned Friedman is standing beside, six enormous trunks ascending to the sky, grew from one of those first seeds, germinated in a greenhouse in the spring of 1948. It could live another 500 years. And it's a monument to a scientific relationship that's outlasted every political storm it's been subjected to. There's also a rather surprising reason why Chinese trees like this one can take root so easily in US soil.

15:04presented by GoTurkiye. Turkiye is a golfer's paradise, and much of that is down to Belek on the country's southern Mediterranean coast. Courses here cut through lush pine forest, set on far, sandy ground that's kept in immaculate condition all year round. And for those never quite ready to call it a day, Belek is also host to the first full 18-hole floodlit course in Europe. Local pro, Denis Satmaz, is lucky enough to call Belek her training ground. There are more than 15 courses. You can play golf in winter and summer. And once the round is done, long lunches replace scorecards and spas, hamams and slow afternoons take over.

15:46When I'm not playing golf, I usually go to the beach, tan, go into the sea. You just feel like you're in another world. Because in Belek, luxury isn't about excess. It's about time well spent. Plan your next detour at goturkia.com today. This is The Documentary from the BBC World Service. I'm Finn Aberdeen and you're listening to The Documentary, Tree of Diplomacy.

16:15Finn Aberdein:Between China and the eastern United States, they share many plans. Because millions of years ago, eastern China and eastern North America was part of one big connected temperate forest. They stay together, living together. You can use the plants to prove the two continents combined together. This shared botanical history explains so much about why this relationship has been able to endure for so many years. I'll chime in on this one. Michael Dostman, keeper of the living collections at the Arnold Arboretum. Eastern North America and Eastern Asia have this incredible shared evolutionary history.

17:04There have been plants that evolved in, let's say, Eastern Asia. Maples, for instance, or viburnos, and shrubs that you might find in your gardens. And then over millions of years, these plants, you know, radiated. They spread across the globe. They continued to evolve and speciate. Of course, the plates were shifting as well. And they sorted themselves out into similar climate types. In fact, the climates of Eastern Asia and Eastern North America are identical, the same types or categories of climates. And so the plants have a pre-adapted nature to them. What Michael means here is that a long time ago, the Eastern United States and China were actually joined as part of the same huge landmass by a giant land bridge.

17:52This eventually became submerged as the glaciers melted. But before it did, plants and animals freely crossed between what are now the US and China. Incredibly, this means that the eastern United States has a startling amount in common, botanically, with China, almost more than it does with the western United States. This geographical phenomenon means that the two countries have a surprising connection when it comes to food, agriculture and the environment. To help facilitate political dialogue around peace in a time of war, to avoid political fear, one has to pick topics that are easier to talk about.

18:40John Kent is co-founder of the Global Supply Chain Diplomacy Initiative, which identifies areas where scientists have established mutual interest and cooperation and builds trade opportunities on the back of them. He's just one example of how policy advisors can make the most of these relationships. So agriculture and food are topics that humanity cares about, no matter what country or what part of a country that you're in, you need food. and so makes a non-controversial, apolitical supply chain to work on. This through line from raw science to policy to processes like trade facilitates peaceful collaboration and has done for decades.

19:30John, for instance, has used mutual agricultural interests in beans, that's coffee beans from Yunnan and soya beans from Arkansas, to forge connections between China and the US with his Peace Beans project. It's the human relationships. I'm talking about diplomacy and goods crossing borders, so soldiers don't. It's a non-governmental way to develop relationships that are built on trust to help smooth out the rough edges that sometimes our governments feel like they have to have because of politics, which sometimes clouds science. These relationships are possible because of the groups like the botanists keeping the door open.

20:17Really a lot of the scientific relationships are really not visible to even to the political system. Dr. Caroline Wagner also sits on the National Academy's subcommittee on US-China scientific engagement. NACPEC is the perfect example of invisibility, right? Foreign ministries don't even know it's there governing and helping botany. NACPEC, the North America-China Plant Exploration Consortium, was formally established in 1991. It's a network of botanical gardens and universities committed to studying, documenting and conserving the plant biodiversity of China. It survived trade wars, diplomatic crises and a global pandemic, and six different US administrations and counting.

21:08Part of that success comes from its stable funding, which is entirely outside of politics. Today, it relies on a network of US and Chinese gardens, private benefactors and conservation funds. But the collaboration goes back much further. One of the first scientific agreements between the two nations was signed almost half a century ago. The 1979 U.S.-China bilateral in science and technology, that agreement was actually pushed initially by Secretary Henry Kissinger, who saw science as a low-conflict area where agreements could be made and that perhaps out of that other kinds of political relationships might develop.

22:00And a year after that new agreement, botanists were among the first to reconnect with one another. In 1980, individual botanists from five American institutions came with a host of Chinese Academy of Science botanists. And they were there in the field collaborating together. And it had been some 25 years, certainly before the Cultural Revolution. Michael Dostman. We had a civil war and World War II was going on. And so it was wonderful in 1980 to bring everybody back together after things started to thaw. And those relationships that were formed there in 1980 took root and followed by multiple Sino-American botanical expeditions in subsequent years.

22:46And that was a great model then that led to the formation of NACPEC formally in 1991. The necessity to physically travel, to work in the soil of another country, creates something that policy agreements and diplomatic cables on their own cannot. Studies show this over and over again, that these trusting scientific relationships endure and are persistent across many difficulties. Dr. Caroline Wagner. People who go into science are usually very much driven by a desire to know and to find something new. And to the extent that they can connect with others with similar interests, those relationships can persist in the face of many different kinds of challenges.

23:34Even as political tensions have ratcheted up and many fields have seen collaboration wither, the relationships already established, rooted in years of face-to-face work, have largely held. Even with the geopolitical storms above, the collaborations continue on below. And we see that even through the Cold War, through many aspects of U.S.-China. Botanical is one of the great examples of that. Early in the days of COVID, I did a study together with Caroline Fry at University of Manoa in Hawaii, where we showed that in the earliest days of COVID, U.S.-China collaboration increased in number. Right?

24:19Why? Because these people had worked together. They had a trusting relationship. They knew one another. And who did they call in the first moments of the crisis? They called each other. And it's true, US, Oxford and China, the three nodes in an already active network were lit up with collaborations in response to the global crisis. To understand what Caroline Wagner means by trust built in the field, you have to go out there with the people who build it. So in 2025, we did a trip to China. Miles Schwartzax is NACPAC's current chair.

25:27meet all of us. I hope I can go to America. Thank you all. I'll remember you all. This is Pan Li from Dejiang University. It's great to know new friends and make new connections. I hope that in the future we can have more collaboration together.

25:53In 2017 when we were in China in Pingwu, we saw one of the largest katsura trees. You couldn't even get three people, four people, five people to stand around it. It was so large. What was fascinating though, is that Ernest Wilson in 1910 saw the exact same tree. He collected seeds from the exact same tree. He photographed the exact same tree. And to be able to visit a plant that Wilson had visited, collect seeds, herbarium specimens, and photographs of the same plant, that stands out as one of the most meaningful in my botanical career. It was awe-inspiring.

26:37In Beijing's National Botanical Garden, the late spring blooming of the tulip trees has coloured the area surrounding the American flora in a constellation of gold and ochre and orange. Wang Kang reflects on the plants.

26:55Finn Aberdein:I can see in the garden there are some American species surrounding me, like American maples and little dungeon, the tulip tree and the ash tree collections. This ash species is a street tree in China, in Beijing. When the time turns to autumn, you can see the beautiful full colour on the street because ash tree species from the United States. The local people like to stay on the tree to have a picnic during the summertime. This experience is mirrored in the eastern United States with Americans picnicking under ginkgos and fringe trees and redwoods. So they have the shared deep evolutionary history, and then they also have the same kind of growing conditions.

27:54And so when I go to East Asia and I'm in a forest, in so many ways it looks as if I'm in the Appalachians in eastern North America.

28:02Finn Aberdein:So that's the reason a lot of scientific botanists working together to have lots of discovery. in recent 100 years. They have lots of research on this kind of collaboration together. That both countries share a botanical culture excites scientists and intensifies the need to work together. My Chinese is practically non-existent. I don't speak very much of it, but I can use the Latin names. And they're using the Latin names, the scientific names. And sometimes there's that root kernel that allows us to communicate. We have the shared knowledge, we have the shared understanding, the shared appreciation for preserving them.