Some see tall skyscrapers and vast networks as symbols of prosperity, but what else have been missed out in the concrete jungle during rapid urban development? This episode explores the story behind the familiar but often neglected stone wall trees on Hong Kong island.

The iconic landscape artifact unique to Hong Kong is a spectacular attraction in the Central and Western district. A row of 15- to 20-meter tall Ficus microcarpa, commonly known as Chinese Banyan, have taken roots and thrived on the vertical surface of historical masonry stone walls.

Kami Hui, the Conservation Manager of the Conservancy Association for 14 years, said stone walls were built when Hong Kong was ceded as a British treaty port. Back then, most Britons resided in the Central and Western district such as Sheung Wan and Kennedy Town. To build houses in the hilly area, the British government flattened the hillside, covered slopes with big rocks such as granite, and filled the gaps between the stones with cement mixture. Such modification gave birth to the stone retaining walls.

Excrement of birds and bats dropped into the gaps of these man-made stone walls has created the most beautiful encounter, as plants would hardly be able to grow from the dry and soilless infertile stone walls, Hui said. When stone walls were met with the seeds of Ficus trees, a strong native species, it became another story. The woody trees have grown from the inside of stone walls with the help of its aerial roots.

“As Ficus grows, its aerial roots take hold too. The trees lignify upon touching the wall or the ground and grow into a part of the impressive structure,” said Hui.

Apart from Ficus, Macaranga tanarius and Celtis sinensis are other common species of stone wall trees. A stone wall tree, if the diameter of its trunk measures around 1 to 1.5 meters, is about 100 to 120 years old.

Stone wall trees survived the Second World War by luck. During the Japanese occupation, plenty of trees in Hong Kong were chopped down and even transported to Japan as construction materials. Hui explained, “Probably because they had not fully grown, or they were seen as invaluable wild plants. Also, it would have taken too much effort to chop down a tree grown above a stone wall.”

So the stone wall trees lived on, for now.

“Dear Paul, a tree on Bonham Road,

Today, an old lady in a minibus asked to be dropped off at the tree she addressed as Paul. That was how I got to know your name.”

It was a love letter to the tree posted on the Facebook page “Dear Tree” founded by Connie Yuen, an illustrator born in the ’80s. She was inspired by the Australian government, which had encouraged people to report on falling trees via email but ended up receiving countless love letters to trees.

Yuen posted love letters people wrote to urban trees on her page, even though some letters are just mumbling about daily life. She also drew maps of trees to help people know more about urban trees. “Some told me they had never realized how important these trees are to them until they saw my Facebook page.”

Living in a concrete jungle like Hong Kong, Yuen believed that as long as people look closely, they would be able to spot plenty of beautiful trees among dense buildings. “A Chinese medicine clinic in Aberdeen was opened below a Ficus tree. Nearby there is a temple built for worshipping Ficus trees. I am not sure if there are more Ficus tree temples in Hong Kong.” She loved the stories between people and trees.

Sadly, urban dwellers often do not realize how protective a tree has been to them until it is torn down. Paul, the tree on Bonham Road, along with its neighboring stone wall trees, began to vanish from the city due to safety concerns five years ago.

Conservation is essential for stone wall trees to survive and grow. Unlike other trees, the preservation of stone wall trees requires different expertise. As an arborist, Hui can inspect the root condition and check if there are any cuts on tree trunks, “but keeping the wall structure safe needs the expertise of engineers”. Professionals from these two areas need to cooperate in order to preserve the century-old stone wall trees, Hui appealed.

Hui suggested that tree planting should be included in the agenda of urban planning at the early stage, to make sure that trees would have enough space to grow. “For example, why do we plant trees along an avenue? Because the rows of canopy are expected to grow big enough to provide shade for pedestrians in 10 to 20 years”

Meanwhile, Yuen believed that urban development requires empathy so as not to limit the growth of trees. “Even humans need space to live, not to mention such huge and heavy trees.” She cited some of Hong Kong’s old public housing estates, where residents can easily take shelter of trees, as a perfect demonstration of how people and trees can co-exist.

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