LONDON.- When Emperor Naruhito and his wife, Empress Masako, of Japan visit Kew Gardens on Thursday as part of a state visit to Britain, the links between their island nation and the famed London landmark will be on full display.

Dotted through the botanic gardens’ 330 acres are constant reminders of that long-standing relationship. In a large greenhouse, bronze sculptures of bonsai trees — some nearly the height of the room — stand in tribute to the Japanese horticultural art form. A short walk away is the Japanese Gateway, an intricately carved cypress replica of a Kyoto temple. Nearby, gravel neatly raked into waves and swirls surrounded by Japanese plant species evokes a traditional tea garden.

Dignitaries and heads of state from many countries regularly stop by Kew Gardens during official tours, joining the crowds that account for roughly 2.3 million visits annually at one of London’s most popular tourist destinations. But, for the emperor and empress, the site will perhaps hold even more relevance.

“We have had a long-standing and close relationship with Japan, which can be seen through several beautiful structures in our landscape, but also in our living collections as well as our economic botany and art collection,” said Richard Deverell, director of Royal Botanic Gardens Kew, the organization that runs the site, recalling the gardens’ monthlong festival in 2021 celebrating the relationship.

The lineage of the emperor, 64, traces back more than 15 centuries, making the Chrysanthemum Throne the world’s oldest monarchy. But much like that of the British royal family, the role of Japan’s imperial family is symbolic and separate from the country’s government.

The tour Thursday is part of a weeklong visit to Britain by the imperial couple, who have long had a personal connection to the country. Both studied at Oxford University in the 1980s — the emperor was crown prince the time; the empress was part of a Japanese foreign ministry program that sends early-career diplomats abroad to study.

The links between Japan and Kew Gardens date to the early 20th century.

Since the early 20th century, the royal and imperial families of Britain and Japan have had a close relationship. In 1902, the two countries signed the Anglo-Japanese Alliance, an agreement that fostered cooperation and cultural exchange.

As British interest about its new ally grew, Japanese art exhibitions became popular; the 1910 Japan-British Exhibition in London drew more than 8 million visitors, according to the Japanese Embassy here. Among them was Queen Mary, who was the wife of King George V and Queen Elizabeth II’s paternal grandmother, and an avid collector of Japanese art.

The ties between Kew Gardens and Japan have continued for generations. The Japanese Gateway — a scaled-down replica of a gate in the Nishi Hongan-ji Temple in Kyoto, made of hinoki cypress — was installed in 1911 after it was shown at the Japan-British Exhibition in London a year earlier.

After the Japanese Gateway was restored in 1996, the temple copy and a new traditional landscape were formally opened by the emperor’s sister, who at the time was Princess Sayako. (She lost her title in 2005, when she married and became a private citizen.) At the dedication, she planted a northern Japanese magnolia, which still grows in Kew Gardens.

The Japanese art of bonsai will be featured during the visit.

The tiny treasures that form part of Kew Gardens’ impressive bonsai collection will be on display when the royal couple tour the historic Temperate House, one of the botanic gardens’ Victorian-era greenhouses.

Bonsai, the growing and shaping of miniature trees in containers, often takes years of work from skilled artists. Among the highlights of the Kew Gardens’ collection of 60 bonsai trees is a tiny specimen that stands just 10 centimeters tall, and another that is 180 years old.

Richard Kernick, a botanical horticulturist at Kew Gardens, said that while bonsai trees are often thought to be dwarf forms, they are actually trees that have been expertly pruned and shaped to prevent them from growing to their full size.

“This intricate and precise art form transforms trees into tiny living treasures,” he said. “A living bonsai is a never-finished artwork that usually outlives its artist. Inheriting a tree is like being a rung on a ladder — there are often many rungs behind and, hopefully, many rungs ahead.”

A series of bronze bonsai sculptures created by British artist Marc Quinn is also featured in the greenhouse, as are some of the rarest plants from around the world.

The emperor will meet with Masumi Yamanaka, the first Japanese residential botanical artist at Kew Gardens, who will talk about her painting of the Miracle Pine, which became a symbol of hope after Japan’s devastating 2011 tsunami.

The visit to Kew is just one stop on the royal tour.

The couple, who arrived in Britain on Saturday, are also spending time with the British royal family. Prince William met them at their hotel Tuesday, at the start of their official visit, and King Charles III and Queen Camilla were to host them at a formal state banquet at Buckingham Palace in the evening.

Charles, 75, and the emperor have much in common — including their sometimes niche interests and the public’s scrutiny of their marriages and obsession with their domestic lives.

Both men are relatively new monarchs. Naruhito became emperor in 2019, when his father, Emperor Akihito, abdicated, and Charles was crowned king in 2022, after the death of his mother, Queen Elizabeth II. On Friday, the last day of their visit, the Japanese royals will visit Oxford.

The emperor and empress have visited several other sites, among them Japan House, a cultural center in London, and the River Thames Barrier, one of the largest movable flood barriers in the world. While the barrier may have seemed like a random stop for a royal, the emperor possibly had more interest in it than many visitors.

The title of his memoir about his two years at Oxford is “The Thames and I,” a nod to the waterway’s effect on his time there and to his college thesis, whose subject was the history of transport on the river in the 18th century.

This article originally appeared in The New York Times.