It's the little things in life: What's driving a bonsai boom in Britain?

It's about intrinsic beauty, inner spirit, a synecdochical relationship with nature. It's also about battling it out on a cold spring morning to see whose tree is tops. Matthew Bell joins Britain's hardcore bonsai enthusiasts – in Swindon, of all places.

There are no forests in Swindon. At least, not for most of the year. But today, in the Stratton Leisure Centre, a few roundabouts out of town, it's as if Birnam Wood has abandoned Dunsinane, headed for Japan and been shrunk in the wash. Welcome to the 10th Anniversary Swindon and District Bonsai Show, the winter highlight of the miniature tree calendar (south-west region).

Lined up on cloth-covered trestle tables are rows of exquisite dwarf trees, each in their own ceramic pot. They are clipped and sculpted and sport distinctive looks: some strike film-star poses, others sit squat and brooding, like broad, twiggy Buddhas. They are stock-still, no breeze ruffling their tiny branches, so that from afar, you might think they were dead. But bonsai trees are a living art form, the result of years of careful grooming.

And judging by the enthusiasts I speak to, it's an addictive hobby. Most have at least 50 trees; others own several hundred. Each tree takes at least 10 years to nurture from seed to maturity, and requires frequent clipping, re-potting and pruning. It's a lot of hard work. So what's the appeal? "Bonsai is about the intrinsic beauty of the tree," says John Armitage, a civil servant from Leeds. "Most people who do it have an affinity with nature. It's not like topiary, creating a blob on a stick: it's about finding the spirit of the tree and bringing that out."

The miniature element is bonsai's defining factor: they should be small enough to carry, and in theory you can keep them indoors. Most bonsai growers keep them outside, however. As one grower says: "You soon find it's easier to keep a tree outside."

For, despite their size, all bonsai start life as normal trees, and any variety can be turned into a bonsai, though the smaller the leaf and slower the growth, the easier it is. The stunting effect is achieved by keeping the sapling in small pots, which restricts growth, and by giving them feed with less nitrogen than normal. Many myths surround the bonsai, and how the practice began. It is widely accepted that it originated in China during the Han k dynasty (206BC to 220AD), but was later popularised by the Japanese, who gave it the name "bonsai", which translates as "tray planting".

The story goes that a Chinese emperor wanted to create a miniature landscape in his courtyard, complete with trees, rivers, hills and valleys to represent his empire, but which would be dinky enough that he could survey the whole thing from his window. It would be a private landscape, for only him to possess: anyone else found owning one would be a threat to his empire, and sentenced to death.

Bonsai first came to the West in the early 20th century, and became more popular as soldiers brought back specimens from Japan after the war. It enjoyed a surge in popularity in the early 1990s, thanks to The Karate Kid, Part III, which featured scenes in a bonsai tree shop. Though it was officially recognised as an art form in Britain in 1935, the Arts Council has so far never granted it any public money. But there is big money in bonsai. According to Armitage, who teaches the art of bonsai, and regularly visits Japan, some trees can fetch £30,000, and tree thefts have increased. "People know bonsai can be worth a lot of money," he says. "They are objects of art like any other. But an opportunistic thief would struggle to sell a tree. The bonsai fraternity is small; everyone knows each other."

This doesn't soothe everyone's qualms: Mark Kerry, 39, is so concerned about the risk of theft that he does not give out his home address. Yet, for him the pleasure of bonsai comes not from their value, but from the chance to get close to nature. "It's that feeling that you can bring a little bit of nature into your flat," he says. "They have an appearance of age, and a real presence. A bonsai tree represents a tiny world of its own; you just lose yourself within it."

Sally May

May had always been interested in trees, when a friend took her to a bonsai show in Bournemouth in 2003. "Between me and my husband, we have more than 100 now. I love their shape and beauty, and the fact that they personify a large tree in a small area. I've got a hornbeam that's my favourite – it has a lovely, crinkly trunk. It's had more and more branches on it in the three years I've had it." The Mays live in Salisbury, and are members of the Swindon Bonsai society. Has bonsai taken over Sally's life? She laughs. "It can be a lot of work. I suppose it has in a way. But not so much, as I also have rabbits."

Italo Volgano

Volgano, a retired hairdresser from Poole, became fascinated with bonsai when he bought his wife a tree for Christmas in 1990. It promptly died. "I ended up with a corpse and didn't know what to do," he says. "A friend's daughter was editor of 'Your Garden' and helped us find a bonsai club in Bournemouth." Volgano, 74, now has 44 trees – though that is well down from a peak of 250. He comes originally from San Gimignano in Tuscany, and says he has been artistic all his life, "styling women's hair. Bonsai trees are similar: in a way, I use the same technique to style them. The fantasy is in my mind. You have to see what a face produces; you have to look at a tree as if it were a person."

Mark Kerry

When Kerry moved into his first house in Berkshire 10 years ago, he was most excited about owning a garden. "I like forests and seeing old trees. Keeping bonsai is an extension of that. Not everyone can live near a forest, but you can bring a bit of nature into your home." The 39-year-old likens the art of bonsai to sculpture. "In fact it's harder. You're not dealing with something immovable – there's the added dimension of a tree changing with time, and you constantly try to improve it." He owns more than 50 trees, and admits that it is addictive. Though it originated in the East, there is, he says, a movement towards a more European-looking bonsai. His particular interest is in creating the appearance of age in a tree: "They're just so intense to look at."

John Trott

Trott was 13 when he saw his first bonsai tree in Shepton Mallet, Somerset. It was 1969, and he was hooked. "There was a private Japanese garden on the lane where I used to walk the dog," he says. "It wasn't open to the public, and had been there since before the First World War." His first tree was an ash, but there were so few books about the subject that he had to teach himself the art. He joined a Bristol group of enthusiasts in the mid-1970s, and his hobby "spiralled" to become his profession: he set up Mendip Bonsai Studio in 1994, and is now a leading dealer, owning a nursery in Shepton Mallet. "There was once reputedly a $1m tree in Japan," he says."It had been in the emperor's collection." His own business is more modest, though he owns "hundreds" of trees. His favourite is still his first, from 43 years ago. "It's nothing really, when you look at it. But that's the one I still hold close to my heart."

John Armitage

In 1985, when he was 12, Armitage discovered a love for Japan. So he took up karate and bonsai at the same time. "I thought the passive would make a good yin-yang fit for the more aggressive side of karate." Today, Armitage is a teacher of bonsai, and travels regularly from his home in Leeds to Japan, to learn from the masters. "Bonsai can be seen as pretentious over here," he says. "But in Japan it's seen as a job, no different to being a gardener. They are more down-to-earth there, and more willing to share. Here you see these so-called grand masters. I would like to change all that." Armitage's day job is as a civil servant in the Ministry of Justice, collecting fines. "My work tends to concentrate on the negative, on people who don't want to pay their fines. So the bonsai is a positive release." And what of the karate? "I gave that up," he laughs. "I learnt that I can only ever do one thing well at a time. I'm quite an obsessive person."