Intrepid orchid-hunter Tom Hart Dyke's passion for plants has led him to some of the most dangerous places in the world.

One trip to find gum trees took him into the heart of the Muslim areas of the Philippines, close to where the Abu Sayyaf group of Islamic militants kidnapped a group of tourists two years ago.

A search for a rare palm led to mined beaches in Cambodia.

However, Tom's trip to the Darien Gap, a notoriously dangerous part of the Colombia-Panama border, populated by left-wing guerrillas, ultra-right paramilitaries and bounty hunters, turned out to be more than even he had bargained for.

Tom, 25, and fellow traveller Paul Winder, 30, a merchant banker from Essex, were seeking rare plants and adventure in the malaria-ridden rainforest and swamp as they set off in March 2000.

Tom wanted to discover a new orchid to name after his grandmother.

The orchid never materialised but they found adventure when they were captured by guerrillas.

For nine months, the men were marched from camp to camp through the jungle, sometimes spending 30 successive days walking along rough jungle trails.

Their captors never revealed their identities nor issued any coherent demands.

Tom said: "The jungles were unimaginable. We were covered in sores, bites, scratches. Once we were up to our waists in a swamp for 36 hours.

"We got foot rot and when you get a scratch it is so humid and fetid that pus forms within an hour. If your clothes rip, the mosquitoes dive on you, biting you so many times it looks like a mound."

Throughout the ordeal the duo tried to see the funny side and keep each other's spirits up, even entertaining themselves and their captors by singing Monty Python's Always Look On The Bright Side of Life.

Tom said: "I know it sounds crazy but we managed to convince them the song was our national anthem.

"We would stand up and sing it and do a little dance. They just didn't know what to make of it. The only way I could deal with it was to talk to the men and women to try to bring out their human side."

The pair were finally released into the jungle, only to be recaptured by another patrol of the left-wing band that same evening.

Tom said: "It was awful. It seemed like we were back to the start, tied up, on our knees, with the butts of their guns pointed at our heads.

"They let us go again but after five days of trekking, covering just half-a-mile a day through swamps, we ran out of food and had to go back to the guerrillas for directions."

Finally, after an eight-day trek, weary and weak, they flagged down a startled Colombian park ranger near the Panamanian border.

Tom said: "I know people say we were irresponsible, I don't have a problem with that, but when you're out there I suppose the adventure just goes to your head.

"A lot of the people who criticise us are the type who only experience adventure by watching travel programmes from their armchairs."

Tom has written a book about his adventures.

His nine-month ordeal in the wilds of South America was a far cry from his expeditions for plants as a child in Ashdown Forest. He spent many happy days roaming through the idyllic forest and hills close to his aunt's home in Upper Hartfield, near East Grinstead.

Tom said: "My aunt had an amazing colony of orchids, which got bigger each year. I would count them each time I went over to visit. It was my uncle's job to mow the lawn and it was my job to stake out the flowers with bamboo sticks. As the colony got bigger, the lawn got smaller.

"Last year there were a couple of thousand plants, a record number, and there is hardly any lawn left."

He puts his love of plants down to his grandmother, who introduced him to gardening at the age of three and was the one who would take him to visit his aunt's house.

He said: "My grandmother gave me a packet of carrot seeds and a trowel when I was tiny and it just grew from there. She started a garden in the grounds of our home.

"She's 88 and you still find her in the flower beds every day with pickaxe and spade. It's what gets her out of bed every day. She is such an inspiration."

Tom watched new Hollywood blockbuster Adaptation, starring Meryl Streep and Nicholas Cage, which is about an orchid-hunter, last week.

He said: "The swamps of Florida are a far cry from the ones we went through in Colombia but I was glad to see the orchid-hunter in the film was even madder than me.

"All the stuff about searching for the ghost orchid is totally true. It's a real passion."

The Cloud Garden - A True Story of Adventure, Survival and Extreme Horticulture, by Tom Hart Dyke and Paul Winder, will be launched at the Orchid Festival at Kew Gardens.