It's November and Hong Kong's bauhinia trees are in full flower. Their branches blaze with gorgeous magenta blooms, adding splashes of tropical colour to the city's streets and parks.

This month also sees the launch of an ambitious project to sequence the genome of the Hong Kong bauhinia tree. Bauhinia Genome is a community-based, crowdfunded venture - the first of its kind in Hong Kong. It's the brainchild of Rob Davidson and Scott Edmunds, two scientists working for BGI, one of the leading genome sequencing organisations in the world. It is headquartered in Shenzhen, but maintains its largest sequencing plant in Tai Po.

When I arrive, I'm surprised to find this state-of-the-art facility housed in a converted print works on an ageing industrial estate. The air here is not scented with flowers, but spiced by the hoisin sauce brewing in the factory next door.

What inspired the idea?

"The Puerto Rican parrot," says Davidson. "I was at a conference and heard about an initiative to sequence its genome, using crowdfunding. It was hugely successful - it boosted peoples' pride in the parrot and their interest in conservation and genetics. I thought it was really cool, and I wondered if we could do something similar in Hong Kong. The bauhinia flower immediately sprang to mind."

The flower of the Bauhinia blakeana tree has been the emblem of Hong Kong since the handover, in 1997. It adorns the territory's flag and is stamped on its coins. Also known as the Hong Kong orchid tree, it is a hybrid - a cross between two other bauhinia trees, Bauhinia variegata and Bauhinia purpurea. Like many hybrids it is sterile, and cannot reproduce naturally.

The Bauhinia Genome team need to raise US$10,000.

"A grass-roots approach has been made possible because the price of genome sequencing has fallen sharply," says Davidson. "The Human Genome Project, which started in 1990, cost US$3 billion and took over a decade to complete. Nowadays it costs US$1,000 to sequence a person's genome, and the process can be carried out in a matter of days."

Decoding the tree's DNA will reveal a wealth of information about the nature of the tree, but the project's aims go far beyond botany.

"We want to engage with the public," says Davidson. "Many Hong Kong people don't understand genetic research and connect it with the scary prospect of 'Frankenstein foods'. They're unaware of the brilliant work being done to cure diseases, tackle global warming and ensure food security. My hope is that by sequencing the bauhinia genome, and getting people involved with our work, we can help to improve knowledge and reduce fear."

According to Edmunds, genome sequencing is one of the technologies that will define the 21st century.

"We're going to see a huge boom in this industry over the next decade, particularly in human health. Fairly soon it will be possible for everyone to have their genome sequenced, in order to fully understand their health issues, and have personalised, precision medicine tailored to their individual genetic make-up. It's vital that people have a better understanding of this technology, because it's going to play such a big part in their lives.

"Hong Kong already has one of the world's best-equipped genome-sequencing centres, so it could become a world leader in this sector."

Talent will be required, as well as technology, and nurturing the next generation of experts is another goal.

"We're getting local university students involved so they can have hands-on experience and learn these incredibly useful skills," says Davidson. "We also want to develop education programmes for schools, to get children motivated and enthusiastic about science."

THE FIRST RECORDED FINDING of a Hong Kong bauhinia took place around 1880. Jean-Marie Delavay, a French Catholic missionary, chanced upon the hybrid while out for a hike in the countryside near Pok Fu Lam.

He took a cutting and planted it at Béthanie, a sanatorium built by the French Fathers of the Missions Etrangères de Paris in 1875. Although it's just off the busy Pokfulam Road, Béthanie is still a calm and tranquil place, with a striking, cream-coloured, neo-gothic chapel, terraced gardens and views out to sea.

Here I meet Francois Dremeaux, a French historian and co-author and editor of the book Hong Kong, French Connections.

"Béthanie catered to French priests from all over Hong Kong and China. When they became sick with tropical diseases, it made no sense for them to travel back to France, so the fathers created this place for them to rest and recover. They chose Pok Fu Lam because it was completely wild and undeveloped back then. It was a quiet place for spiritual retreat and physical healing."

The missionaries, however, were not inclined to spend their days relaxing.

"They were men of action. They had all committed to spend their lives evangelising in China - a decision which required an adventurous spirit, as well as religious conviction."

The missionaries found ways to lead constructive lives while recuperating. They built a printing press nearby, developed a large, productive market garden, experimented with crop varieties and carried out scientific research. It was within this context that Delavay, on spotting the beautiful bauhinia, took a cutting, cultivated it and - unknowingly - secured its place in Hong Kong's history.

A few years later, a cutting from Béthanie was given to the Botanical Gardens. Here, the plant received its scientific name. " Bauhinia" paid tribute to the Bauhin brothers, Gaspard and Jean, a pair of 17th-century French-Swiss botanists. " Blakeana" honoured Sir Henry Blake, the then recently departed governor of the colony and a keen botanist.

The first scientific description was written by Stephen Troyte Dunn, superintendent of the Botanical and Forestry Department, in the Journal of Botany, British and Foreign, in 1908: "The tree is at present a very rare one in cultivation and is likely for some time to remain so, as it can only be cultivated by cuttings. This is the more to be regretted because out of the numerous cultivated species of this charming family there is probably none that equals it either in the beauty or the profusion of its flowers."

The tree has not changed since Dunn's time - to this day it can "only be cultivated by cuttings" and is entirely reliant on its human guardians for propagation. However it is no longer "very rare". Its beauty has ensured its survival.

The Hong Kong bauhinia has been planted all over the territory, with 25,000 trees under the management of the Leisure and Cultural Services Department alone. It has also migrated overseas. When Delavay returned to his mission in Canton (Guangzhou), he took cuttings with him. The bauhinia now lines many roadsides in southern China; the trunks are painted white and the treetops arch together over the tarmac to create a spectacular tunnel when in flower. It is also a popular landscaping plant in the southern United States and Australia.

Keen to see some bauhinia trees, I head to the University of Hong Kong to meet Lawrence Ramsden, honorary assistant professor in the School of Biological Sciences and a bauhinia enthusiast. We take a stroll though the grounds and Ramsden points out the Bauhinia blakeana trees and their two parent species. Bauhinia variegata has flowers ranging from pale pink to white, some with a bluish tone. The flowers of Bauhinia purpurea range from rose pink to white with more of a purple tinge, as the name suggests. In all other respects - the leaves, the bark and the shape of the petals and flowers - the three trees look very similar.

The Bauhinia blakeana discovered by Delavay is the only one that has ever been found growing wild. I wonder if that was the only time the two parent species produced a hybrid offspring naturally - could it have been a one-off event?

"It's a question which fascinates me," says Ramsden. "If I had the time and money to get samples from all over the world, and test them, I'd love to do that. For the moment it remains a hypothesis that every Bauhinia blakeana tree in existence is a descendant of that single individual. Every plant we've tested so far is - we know this because they are all clones [genetically identical to each other]. So it's definitely a possibility."

Ramsden explains how the trees are cultivated.

"The gardener makes a V-shaped cleft in the root of one of the parent species, carves a corresponding wedge shape at the tip of a blakeana shoot, and slots it in. The two are bound together with tape. With luck, the two plants fuse together and grow."

Being sterile, the Hong Kong bauhinia does not produce seeds but there are precedents, in other plants, of sterile hybrids gaining this ability. Ramsden has long hoped to find a Bauhinia blakeana that has undergone this change, because it would make growing the trees less laborious.

"At the moment cultivation is mostly restricted to commercial planting. If we had seeds, then domestic gardeners could plant them, too."

Some years ago he mounted a project in which secondary school students, armed with identification guides, located Hong Kong bauhinia trees, marked their position on a map and checked them carefully for seeds. No seeds were found, but Ramsden has not given up hope.

"I still get occasional reports from both Hong Kong and overseas. I had a report of a tree with seeds from Greece this year, and another from the United States, but I haven't received samples from either yet."

In 2005, Ramsden and his colleagues produced the first scientific proof that Bauhinia blakeana is the hybrid offspring of the two parent species. They used a technique that analyses genetic markers - ancestral footprints in the plant's DNA. The Bauhinia Genome project will also explore the plant's hybrid nature, but in much greater depth. I head back to BGI to find out how.

"We're planning to sequence the whole family," says Davidson. "Plants are challenging because they have very complex genomes, and the Bauhinia blakeana is especially tricky because it's a hybrid. It was built in nature by sticking the two parents together, so the best approach for us is to reproduce that in the lab - by looking at the two parents first and then working out how they made their offspring."

Edmunds takes me to see the sequencing floor. We wear lab coats and plastic shoe covers, just to look through the windows.

"It's all carefully controlled to reduce the risk of samples becoming contaminated with DNA from other sources, including ourselves," he says.

Off a long corridor are a series of laboratories on either side, furnished with long metal work benches and kitted out with centrifuge machines, racks of test tubes, piles of petri dishes and huge plastic containers containing liquid chemicals.

Edmunds explains that the first step is to extract the DNA from the bauhinia leaves and flowers. The genetic material will then be moved along the corridor, from one laboratory to the next, undergoing a different process in each. Along the way, the DNA will be broken into small fragments, and stuck to glass slides. Finally, it will arrive at the sequencing room, where BGI keeps its 55 sequencing machines.

"This is where we turn life into data," he says.

The glass slides slot into a machine that reads the DNA. It generates a vast quantity of data, which is collected in BGI's computer centre, a sealed, climate-controlled room with banks of servers, tangles of wires and lots of flashing lights.

The raw data consists of millions of fragments. The next task is to match these up to recreate the trees' genomes.

"It's like building an enormous jigsaw puzzle by working out how all the tiny pieces fit together," Edmunds explains.

My final port of call is the Chinese University of Hong Kong, where Kwan Hoi-shan, a professor in the School of Life Sciences and one of the collaborators on the project, will marshal students to do the bulk of this assembly work.

"BGI will upload the data to an online platform that's open to the public, so anyone in the world who'd like to get involved can also contribute," he says.

Once assembled, the genomes will be analysed. Kwan plans to investigate claims that Bauhinia purpurea - which is used in traditional preparations to treat ulcers, wounds and tumours in India and Pakistan - has genuine medicinal properties.

With knowledge of the genome, the team can also assess whether the trees are able to withstand epidemics. As a clone, the Hong Kong bauhinia may be vulnerable to disease - if one tree lacks natural resistance, all the others will, too.

"Knowing the genetic make-up could be extremely useful, and there might be the possibility of adding or editing genes to confer resistance," says Kwan.

The primary focus, though, will be to examine the Hong Kong bauhinia tree's evolutionary past, to find out if the story revealed by the genome matches the one recorded in the history books.

"If we go really deep, we'll be able to pinpoint the time and place of its origin, and confirm if it's truly a native of Hong Kong. With enough samples, we could discern if other wild hybrids have occurred, or whether that single tree from Pok Fu Lam really did give rise to all the trees alive today."

For more information on the Bauhinia Genome project, visit igg.me/at/bauhinia.

 

Creating the winning design for Hong Kong's postcolonial flag

The bauhinia flower became a cultural icon when it was selected to be Hong Kong's postcolonial emblem in the run-up to reunification with China. At the handover, in 1997, the Blue Ensign flag that had been flown during the colonial era was retired and the bauhinia was raised. From 1993, the flower supplanted the Queen's head on the city's coins.

In 1987, a contest to design the new flag and emblem was launched. An 11-member panel, including government officials from Hong Kong and the mainland, artists and designers, businesspeople and a sporting body representative (because of the role flags play in international fixtures), was appointed to judge the submissions.

From 7,147 entries, which arrived from all over the world, the panel shortlisted 52 and then whittled it down to 12 - six flags and six emblems. These were passed to the 59-strong Basic Law Drafting Committee, which was charged with choosing one from each category to submit to Beijing for approval. However, none of the designs earned the required two-thirds majority. Instead, three of the Hong Kong panel members - artist and designer Hon Bing-wah, sculptor Van Lau and architect Tao Ho - were asked to come up with a new design.

"It was really difficult to decide on the right design," says Hon, at his art gallery, HS Modernart, in Repulse Bay. "Hong Kong is a region of China - it's not its own country. We couldn't choose a classic tricolour, striped design, because those flags are typical of European countries with long histories. As the same time, it couldn't look overtly communist in style."

The trio met in Guangzhou, along with the heads of the judging panel, for a brainstorming session.

"We knew we needed a pattern for the centre of the flag," says Hon.

The team reviewed the competition submissions for inspiration.

Dragons were a popular suggestion but the team felt they were too traditional, and that the new special administrative region merited a modern design.

"Another issue with dragons was that they have a different resonance in different countries - it's not an easy symbol in an international context," explains Hon.

A junk boat was another obvious option, but had to be rejected because it was already used as the symbol of the Hong Kong Tourist Association (which would become the Hong Kong Tourism Board in 2001).

"We wanted something simple, elegant and striking, and we discussed the fact that Hong Kong people like nature," says Hon. "We have many wild animals in Hong Kong, but we couldn't use something like a monkey or a dolphin."

He perused flags from around the world and found himself drawn to Canada's flag, with its red maple leaf. It slowly became clear that the bauhinia flower was the right choice.

The only sticking point was that the Urban Council - the body responsible for municipal services on Hong Kong Island and in Kowloon (and which was dissolved during government restructuring in 1999) - had adopted the bauhinia as its emblem in 1965.

"The Urban Council's bauhinia was designed in a symmetrical, static way," says Hon. "We decided to make ours look much more dynamic." Hon had the idea to represent the bauhinia in a windmill style, so that it looks as if it is spinning. "I was inspired by the decorative motifs of Chinese paper cutting. In this tradition it's common to find rotating patterns. They give a feeling of movement and are auspicious, because they represent prosperity and growth."

The team produced three bauhinia-design submissions. Ho's entry was endorsed by 34 of the Basic Law Drafting Committee members and selected. The design was accepted by the central government at the seventh National People's Congress, in Beijing, in 1990.

Ji Pengfei, the Drafting Committee's chairman, explained the flag's design at the congress: "The red flag represents the motherland and the bauhinia represents Hong Kong. The design implies that Hong Kong is an inalienable part of China and prospers in the embrace of the motherland. The five stars on the flower symbolise the fact that all Hong Kong compatriots love their motherland, while the red and white colours embody the principle of 'one country, two systems.'"

The red shade - a festive colour, used to convey a feeling of celebration and nationalistic sentiment - exactly matches that of the flag of the People's Republic of China. The five-pointed stars - one on each petal - also echo those of the Chinese flag, on which they represent the Communist Party and Mao Zedong's four social classes (proletarian workers, peasants, petty bourgeoisie and capitalists). On the Hong Kong version, the stars are all the same size whereas on the Chinese flag the Communist Party's star is significantly larger, outshining the other four.

The new flag was officially hoisted for the first time seconds after midnight on July 1, 1997. Just before the big hand struck 12, the Union and colonial Hong Kong flags were lowered.

With the raising of the bauhinia flag, the sovereignty of Hong Kong was transferred.