Evergreen tree ferns thrive in sheltered city gardens and remind Osborn of life in New Zealand; Pelargonium ‘Marquis of Bute’, rightCREDIT: Marianne Majerus /Andrea JonesWhile studying to be a national park ranger, Osborn spent his holidays undertaking surveys of flora and fauna in the remote bush for the forestry service. “You were flown by helicopter into the mountains and left to find your way out after three months of feral living,” he says.“

These were very remote areas where people might have been, but no one had ever stepped where you stepped before.”“New Zealanders are used to roughing it,” he continues, with droll humour. “I travelled overland from south-east Asia to London over 23 months, bumping around in a dusty old bus, up into Nepal and through Iran in the 1980s. In Rome I slept behind statues and ate apples picked up off the street, but I knew that once I got to England I could probably find work.”

Arriving in the harsh winter of 1982, Osborn delighted in exploring the metropolis by trudging through the snow in ever-expanding circles from his digs in Cricklewood until he discovered how to buy a bus pass. “I found it was almost like being in a forest here because you can only see to the end of the road,” he recalls, “each street is like a little valley and that led to my idea that London is a forest, and my realisation that shade-loving woodland plants would work well here.”

Yet it would be years before Osborn rekindled his childhood love of horticulture; instead he worked for a marquee company and studied international trade at Westminster University –until, one day, the sight of a tree fern at a nursery in Battersea triggered a personal revelation.“I told them about how I slept under the branches of ferns in the New Zealand bush and how the spiral of fronds symbolises the unfurling of life in Polynesian art,” he says.

The owner of the nursery offered to introduce Osborn to all her customers if he could organise the import of tree ferns (which requires aCITES certificate) –and he never looked back.“My tree ferns come from forests that are due to be milled for the timber industry, so [exporting the trees] means they live rather than die,” Osborn assures me. “Once the forest is replanted, the spores blow on the wind, permitting the ferns to colonise it again and regenerate.”

In need of space for the tree ferns, he recalled a nursery where the marquee business had stored their tents. He approached Alan Mellenfield atLeahurst Nurseriesin High Barnet. “He was a nurseryman all his life, a bedding plants person; he could notbelieve itwhen I arrived with 800 monstrous tree ferns,” Osborn remembers gleefully.When he headed toColumbia Road flower marketin Bethnal Green to sell his ferns, Osborn never realised how profoundly it would affect his horticultural practice.

"I have great respect for East End people,” he says, “they gave me a community that otherwise would have been missing in my life. To go there each Sunday is the highlight of myweek.”Before long Osborn was also selling bedding plants alongside his tree ferns and, when Andrew Mellenfield retired, he took over the nursery.“

Columbia Road gave me exposure to the landscapers, the jobbing gardeners and the bulk purchasers of plants,” he says. “Very early on I met Todd Longstaffe-Gowan, gardens advisor to theHistoric Royal Palaces. He said, ‘You’ll get to meet every lord and lady in the country’ and I just about have. We have worked on a lot of landscape projects together using my plants.”These prestigious projects, which include maintaining the gardens at Spencer House, are a source of pride for Osborn. “

The Rothschilds came to my nursery to check the provenance of the tree ferns because they are a great horticultural family,” he reveals. “Waddesdon Manorhad its own nursery for many years. They see me as one of the old school jobbing gardeners of the Victorian era.”Alfred Dunhill’s is a particular favourite of Osborn’s. “As a men’s club, they are not prissy with their planting, we use strong colours and if there’s a dead flower they don’t notice.

We plant it and don’t go back for four months, we let it go wild. One year we planted a parterre with flowers and vegetables, and every cabbage white in London decided to gather in Mayfair and decimate the whole thing. It was just stalks left with flocks of butterflies.“I rang them up and said, ‘We’ll come down and replant this,’ but they said, ‘No, it’s wonderful. There’s crowds outside admiring the butterflies.’”In his nursery, Osborn favours propagating original species and unusual oldvarieties with subtle rich hues, like‘Marquis of Bute’. “They have stood the test of time, they may not have theblowsy colours of modern cultivars but they are more hardy and disease resistant.”Being a nurseryman has confronted Osborn with the challenges of the industry, a subject which fills him with evangelical emotion. “

The British are the most enthusiastic gardeners on the planet yet we import our plants from Europe when we once had own industry. Do people realise where their plants are coming from and the problems with such a supply line?” he demands. “You have only to drive around the countryside to see the abandoned glasshouse with trees growing through them. We need to grow more plants ourselves.”