Paradise in Camberwell: A gardener has created an extraordinary home for tree ferns in London

Patrick de Nangle has turned his garden into a jungle of tree ferns, cycads and bird-of-paradise plants

Patrick de Nangle's carefully nursed tree ferns, 'Cyathea australis' (Richard Mildenhall)

I didn't have to look very hard for Patrick de Nangle's garden at 8 Calais Street in London's Camberwell, which is open tomorrow for the National Gardens Scheme. A huge Chusan palm was spraying its fronds over the well-camouflaged wheelie bin. The shine on the leaves of the banana plant in the front corner dazzled the eye.

Elegant umbrella fronds of tree fern arched over the low box hedge that bordered the path to the front door. All the plants – the vast hosta, the acanthus, the shrubby spurge – were thumping with vigour and delight. I wanted to drag every single member of the local council past the litter and the derelict façades to stand in front of this house. "Look," I'd say. "Look what a difference a garden makes."

Meanwhile, de Nangle, single-handed, is doing his best to green-up the neighbourhood. He paid for the old mattresses to be cleared out of the front garden of the council-owned house next door and, along with the tenants, planted the garden with more tropical exotics. He adopted the white gravel waste in front of the house on the other side and put in the echiums and phormiums that he couldn't fit into his own patch. And then he started on the nearest roundabout: more huge echium rosettes, which I'd clocked as I walked down from the Oval Tube station. "Strange," I'd thought. "That doesn't look like the hand of a municipal authority." And after I'd met de Nangle, I learnt of course that it wasn't.

"I put out some nice golden phormiums there," he said. "I thought they'd get nicked, but they haven't." People passing on bikes shout out encouragement as he's doing his guerrilla gardening. Cars beep. Where will it all end?

But the real marvel is de Nangle's own back garden, not more than 100ft x 45ft, which he has turned into a jungle of tree ferns, 25 or perhaps 30 of them, soaring up from a lush green carpet of mind-your-own business (Soleirolia soleirolii) which stretches right across from one wooden-boarded boundary to the other. Banked round the edges of the garden are cycads, bird-of-paradise plants with strong paddle-like leaves, cannas, bird's nest ferns. A lilac in the back corner, the only thing left over from what was here before, now looks like a granny trapped by mistake at a rave.

What strikes me about this garden is not just how astonishing it looks, but how beautifully the plants are cared for. You can feel it as you walk among them. Anyone can spend £500 on a tree fern and stick it in the ground. But to understand its needs, to keep it looking beautiful, year after year, that's another thing. Several times he's rescued seemingly dead tree fern trunks from skips and brought them home. Sometimes, after months of care, he's managed to coax them back into life. And so his forest grew.

Patrick de Nangle tending his garden (Richard Mildenhall)

The most recent additions are not the most commonly planted tree fern, Dicksonia antarctica, but two Cyathea australis, both 12ft high, promised by a fern dealer in east London's Columbia Road market. "They needed to be high," he explained, "so they didn't collide with the tree ferns that are already here." They arrived in June this year, much later than he'd hoped, showing no signs of life. For each tree, he excavated a hole the size of a frig (cyatheas have rootballs whereas dicksonias do not), got them upright, and then almost every day climbed up his tall decorator's ladder to pour warm water into the crown of each plant, 12ft off the ground.

After two months, one of the ferns responded to his TLC. The other is only just now breaking into growth. By the time its fronds (lighter, more elegant and even longer than those of dicksonia) are fully expanded, he'll be worrying about protecting them for the winter. Actually, here, in south London, he finds that a few handfuls of straw or leaves in the crown has usually been enough. In the wild, his cyatheas grow in the same areas as the dicksonias, but at higher altitudes and in more open sites. So, in theory at least, they should be no more tender than their cousins.

"Where did it all start?" I wondered, but de Nangle couldn't remember a time when he hadn't gardened. "I kept the parents' garden lovely," he says. That was on the family farm in Co Laois, in the middle of Ireland, where he gathered up seedling birches from the bog and brought them home in a sack to plant in the lawn. At college, his father insisted he study agriculture, not horticulture, but by his early thirties, he'd had enough of farming and took off for the States. Even there, in a studio flat in Manhattan, he rescued thrown out pot plants and coaxed them back to beauty.

Perhaps it was on a visit to Hawaii, he says, that this most unlikely Camberwell scenario was first imprinted on his mind: tree ferns 50ft tall growing up from a carpet of damp moss, everything green and lush. And then Eric, in the Columbia Road market, wanted to get rid of two 6ft tree ferns at a bargain price, and he was away. But in Hawaii, nature produces the conditions the plants need. In Camberwell, he has to. Constant watering. Masses of feeding (he uses fish meal for long-term sustenance, Miracle-Gro for a more instant boost).

Sometimes, he says, he fantasises about going back to Ireland. Not to Co Laois, but somewhere down in the southwest, Co Cork perhaps. Somewhere with about 10 acres of land and a stream. He'd hire a truck and take all his tree ferns with him and there, in his 10 acres, he'd be able to give them more room to spread and express their beauty. Meanwhile, don't miss the opportunity to see Patrick de Nangle's extraordinary garden, open tomorrow (2-5.30pm), admission £3.50.