'My best find was in a skip': Wayne Amiel reveals his dedication to abandoned plants

I used to know the streets round London's Clapham Old Town reasonably well, wheeling pushchairs past the grand façades of The Pavement, balancing small children on swings in Grafton Square, haring after scooters in Rectory Gardens. Someone once told me this was the oldest squat in London. I like Rectory Gardens – the random collections of stuff tacked on to walls, the small bits of garden laid straight on to the street, shored up with timber offcuts, casually, promiscuously planted with marigolds and lettuce, petunias and parsley.

The layout of city streets like these in south-west London rarely allows you to see what's going on in people's gardens, hidden at the backs of the houses. Many of the terraces front straight on to the pavement; where there are patches in front of the houses, as in Grafton Square, they are treated in a fairly minimal fashion. Sometimes you see a big pear tree in a back garden, rearing up over the slope of a roof. If I catch a glimpse of one, I cheer. The odds against the survival of these old trees, remnants of the orchards and market gardens that once ringed London, are now huge.

The levels catch you out, too. Sometimes you go up steps to a front door, but then have to plunge down at the back to access the garden space. Sometimes the garden is at the same level as the front hall. You haven't any idea when you step into a house what you are going to emerge into on the other side. It's like being Alice as she goes through the mirror. And never more so, for me, than at Wayne Amiel's place in Turret Grove, a pretty street in Clapham Old Town, that runs down the hill from Rectory Grove to North Street.

Amiel describes it as "Clapham meets Jamaica", with the wild, bold colours off the Caribbean jostling side by side with English favourites such as sweet peas. Yes, it's all of that, wonderfully exuberant, but what struck me first was the way that the garden sailed high above its neighbours on either side. Very private, ringed round with greenery and completely over-the-top lilies, it's suspended but secluded too, a difficult double act to bring off.

Sitting in the semi-basement kitchen/dining room at the back of the house, you don't see any of this. At this bottom level, Amiel added a glass-roof extension which opens out on to a series of wide, very steep steps that, if you were brave enough to tackle them, would bring you out into the main garden above. But from inside, what you see is a dazzling array of pots lined out at each level: pelargoniums, hostas, impatiens, cosmos, petunias. "It's my homage to Amsterdam Flower Market," says Amiel. "I used to go there every morning, have a coffee, read the paper. My idea of heaven."

But I'm wondering how he gets all these things to flower so well. This is a north-facing garden, just 65ft long by 25ft wide, and the steps don't get much sun. "I've got a sick bay at the back of the garden," he explains. "A table in my only sunny corner. All the pots get a holiday there to cheer them up, and bring the plants into flower." It turns out that Amiel is up by about half past four each morning, spends an hour and a half in the garden, then goes to the gym for an hour before leaving for work (he's a manager in the NHS).

So, quite a driven man, I enquire rather unnecessarily? "You could say so, but I just love my garden. I love my flowers. I especially love to buy things on the 'damaged' stand at the garden centre and nurse them back to health. My best find was in a skip – a lilac. It was just a twig, but it's turned into a fabulous thing, deep purple gorgeousness."

We've come up the stairs from the semi-basement now and are standing on a deck adjoining the back of the house, from where you can look down on the rows of plants on the steps below. The deck is surrounded by greenery: fat hostas, a tall tree fern. There's abutilon and strawberries, fabulous gerberas, masses of herbs, twisty willow, brightly patterned coleus, grown from seed. "I grow a lot from seed, take cuttings. The box room upstairs is a kind of potting shed and in the winter every mantelshelf is lined up with plants that can't stay out in the cold."

There are cornflowers, geums, an elegant purple-leaved acer and a trachelospermum scrambling up the arch that separates the first deck from a second, smaller decked area beyond. Most of the plants seem to be in pots. "How many pots," I ask. "More than two hundred," Amiel replies. "I gave up counting." He makes his own compost in a beehive-shaped bin, and mixes this with bought-in compost and sand for his planting.

The trees – twisty willow, acers, weeping silver birch, robinia – are root-pruned every three years. Some are planted in the ground, rather than pots, but Amiel reckons he's helped by the fact that an Anderson air-raid shelter stretches under much of his plot. The layer of earth on top is quite thin and this keeps the trees to a manageable size.

Beyond the second deck is a circular lawn, edged with brick. "It used to be much bigger, but I kept nibbling away at it to find room for more plants." But what about watering all this lot, I ask, waving a hand round the extravagant pots of lilies, the dahlias, ferns, the hops and passion flower smothering the fence, the gunnera and bamboo, the bright photinia, the foxgloves and fig, the hostas with leaves as big as ponchos? "Oh, I love watering," he says. "It's really relaxing after a stressful day at work. And I prefer using a watering can to a hose. You can give each plant just what it needs."

After spending five years building up this amazing garden, Amiel is opening it for the first time. You can visit tomorrow, between 10am-5pm, admission £3. A bargain.