But the hydroponics retailers, who call themselves 'grow shops', are worried about their bad press, and about rumours of a legal clampdown on their trade. What is good for tomatoes and oranges is also proving unlawfully fertile for growing cannabis.
The retailers find themselves facing two ways at once. While claiming that they are catering for the legitimate demand of gardeners, they are nevertheless advertising in magazines such as Viz to attract the 'grow your own, and then smoke your own' customer.
Iain Reynolds is a director of GroWell Hydroponics, a recently formed workers' co-operative in Coventry. He said they were targeting serious gardeners with their promotion, and had taken a positive decision not to seek the 'hippy' customer. But, he added: 'We have had to advertise in drug- orientated magazines as well, so as not to lose business.'
Whether the grow shops target cannabis or not, it too is proving big business. A recent raid in Essex found 1,500 cannabis plants being grown, worth about pounds 1m. Police say that hydroponically grown plants are proving an increasing problem. Hydroponics can enable a plant to grow up to four times more productively because, with water-based nutrients feeding it regularly, it does not need to divert its energy into a large root system. Large lofts across the country are becoming mini drug factories, it seems.
It is rumoured that the police are asking for a change in the law to make the sale of hemp seeds illegal (it is currently legal to buy the seeds, but not to grow the plants for consumption). Some police forces also want powers to force grow shops to notify them of all sales of equipment - something that is worrying the retailers. A spokeswoman for the Home Office says it has no plans to amend existing laws.
Mr Reynolds says that attention should focus on what an efficient system hydroponics is for all types of plant. It is proving very popular now with market gardeners.
'It means you can grow plants anywhere - in deserts, on a spaceship, on an oilrig, in a room without a light, or in a coal mine. It's been around a long time - the Hanging Gardens of Babylon appear to have used hydroponics.
'And it reduces the use of water, to about 10 per cent of that for gardening, where most just goes back into the water table. That could be a real issue in the future with the prospect of water metering.' Hydroponically grown plants should also be healthier, by avoiding soil- based disease.
All that is needed to start gardening hydroponically is a growing medium which substitutes for soil, plus nutrients, seed and pots, which can be bought for less than pounds 20. For those who want to move on to converting the loft, it may be necessary to pay pounds 200 for a 400- watt light large enough for a container of 10 to 15 square feet. After that, the only thing to worry about is the size of the quarterly electricity bill.
For some people, the excitement of picking a home-grown strawberry at Christmas may be enough to make the cost and trouble worth while. But there may be even more whose main motive is to cut the cost - and avoid the growing risks - of street dealing.