They're at it all over the country: middle-class professionals, turning gardens and linen cupboards into mini cannabis plantations. Jim White skins up
Here is a modern ethical dilemma. Dave, 42, a bigwig in advertising, took his wife, Jan, a television producer, on a short break to a country hotel recently. They left their 15-year-old son, Dan, in Wandsworth, south London to guard the family fort. When they returned they discovered that, in the tradition of home-alone teenagers, Dan had hosted a weekender. But this was not a minor bring-a-bottle affair: Dan had harvested all four of his dad's cannabis plants, items Dave had nurtured with pride and attention over the summer, popped the crop of leaves in the microwave and then proceeded to smoke the lot with his chums.

"I was absolutely fuming," says Dave. "What was I supposed to do? Bollock him for smoking grass when I'm growing the stuff in the back garden? In the end I gave him a lecture on impatience: if he'd waited a month or so, there would have been a lot more for everybody."

Which is true. This summer, provided plenty of the local water authority's product was used, cannabis planted in gardens, window boxes and greenhouses grew at about an inch a day; rich, thick and glossy growths were peeping over the nation's hedges and fences like unruly pubic hairs escaping from swimming costumes.

"Vintage year," says Alan, 37, another ad exec who had a crop on his window ledge in Highgate, north London. "I filled three washing-up bowls with leaves from one plant."

For obvious reasons, it is impossible to estimate the amount of cannabis being home-cultivated in Britain, but anecdotal evidence suggests it is challenging tomatoes as the nation's favourite bit of small-scale horticulture.

For one group of people, growing your own satisfies two significant needs. If you have reached a certain station in life, you don't wish to engage with the black market, where you run the risk of beingarrested or ripped off. Also, growing your own fulfils the urge to propagate, to till and cultivate, an impulse that overcomes many people when they reach a certain age.

"There's a nice, hippyish, self-sufficient feeling to growing your own that contrasts with the life you lead now," says Jonathan, 39, an academic in Cambridge. "It's a bit like making your own bread: completely unnecessary but disproportionately satisfying. I usually take a bag along to dinner parties. People seem to appreciate it more than a bottle of claret."

Although it is illegal to grow cannabis, by one of those quirks of law it is not illegal to sell, pass on or otherwise supply the seeds. Thus, last May, when the editors of Isis, the Oxford student magazine, stuck a packet of 20 seeds to the front of every copy as a sales promotion device, Sergeant Henry Wymbs of the Oxford police, called in by the university authorities to intervene, was moved to say: "It is not illegal for the magazine to provide seeds but anyone planting them will be committing an offence."

Cannabis seeds are available by mail order from all sorts of places, but principally from the classified ads in the back of the magazine High Time. Also widely available are the grow-lamps and hydroponics equipment for indoor, water-based nurture much favoured by those without gardens or with nosey neighbours. Hydroponics kits sufficient for up to 12 plants are available from Hydrosystems, Castleford, West Yorkshire (01977 604065) for pounds 250. It is not illegal to sell this stuff because it is also used to help to grow tomatoes and leeks.

"The lights are fantastic," enthuses Alan. "One of my plants on the window sill reached 8ft 11in. It hit the ceiling and turned right. I had a grow-light positioned above it, and one night I was coming back from the pub and I saw this light and this massive growth in the window and I thought, blimey, someone's got a Christmas tree up and it's only October. Then I realised it was my plant. And I hadn't even smoked any of it yet."

There are all sorts of propagation tips and legends that circulate among growers. Pricking the stem - thus fooling the plant into thinking it is under attack and encouraging it to produce more in self-defence - is a favourite.

Steve, a 39-year-old comedian from Brixton, has heard most of the handy advice. "This old hippie who lives on a bus in Lincolnshire told me that if you really want to grow giggly stuff, you should cover the plants at night for 12 hours with bin-liners. They thrive better if they have an exact balance of light and dark," he says.

The other tip is how to avoid the police. One paranoid conspiracy theory has it that helicopters with heat-seeking cameras flap across Wales on the look-out for lamps. This is an unlikely waste of a precious police resource otherwise required to make videos of car chases for television shows. Another has it that electricity companies tip off the force when they detect the sort ofincrease in usage that suggests grow-lamps are in operation. This, too, is not possible, since the Data Protection Act ensures the confidentiality of bills.

Nevertheless a disproportionate number of home-growers seem to have yarns about brushes with the law. "I had a policewoman knock on the door once to give advice on anti-burglary devices," recalls Steve. "I'm a bit of a sucker for a uniform, so we got chatting and I invited her in to have a look at my security arrangements. I led her into the kitchen and she started looking at the back door. Then I suddenly realised that there were four cannabis plants on the patio. Too late, she opened the door, took one look at the plants and said: 'You want my advice?' I thought: 'Here we go'. And she said: 'They like a bit of damp, they'd grow much better in the bathroom.' "

More terrifying for the grower, however, are brushes with real authority figures: mothers with a pre-rock 'n' roll era attitude. "My mum and my younger sister were due to come to stay," Alan recalls. "I had this massive plant filling the bay window in my front room. The choice was: do I harvest it early, and sacrifice a good few smokes, or do I bank on my mum not knowing what it was? I left it and she was rather admiring of it, asked me what it was. I said I didn't know, I'd inherited it off the bloke who owned the house previously. My mum asked if she could take a cutting back to my dad. And I'd forgotten about my sister, who was about 17 at the time. She said: 'No, Mum, you can't grow dope from a cutting - you need the seed.' "

Not a problem, presumably, that Dave from Wandsworth and his son Dan will ever face.

For obvious reasons, all names in this article have been changed.