From Kenya with love

Dust rises on Main Street, Naivasha, Kenya: banks, hotels and houses with verandas are under construction. Signwriters paint advertisements on to whitewashed concrete walls: Hardware, Driving Lessons, Hair Extensions, Lake Place Night Club.

Naivasha is a boom town built on a new gold rush: cut flowers.

As you read this, 25,000 workers are picking roses for Valentine's Day bouquets thousands of miles away. Greenhouses each a hectare in size line the road to Lake Naivasha. On these shores Lord Errol's Djinn Palace hosted the debauchery of the Happy Valley set and Imperial Airplanes seaplanes were a regular sight. Today the road is asphalted smooth and flat so that truckloads of roses will arrive unbruised at Nairobi airport, which has a terminal purpose-built for the export of flowers and vegetables. In 20 years cut flowers have sprung up to join tourism and tea as one of Kenya's biggest employers and exports.

Floriculture is an equation between the life - or, rather, living death - of a cut flower, and the time required to get it to market. Rail links to London brought the Lincolnshire bulb fields into being; in 1896 a new hall was built at Covent Garden for carnations whistled overnight from the French Riviera. And in 1969, American entrepreneurs hired a cargo plane to airfreight flowers from Colombia: on the equator roses flower all year round. Today, the international cut-flower trade is estimated at $60?billion a year.

Roses for rhinos

I am in Kenya as a guest of Waitrose, which has sponsored Floriculture: Flowers, Love and Money, an exhibition at the Garden Museum in London which tells the story of the rise and fall of British floriculture. And, we hope, its revival. Today, just 10 per cent of the flowers we buy are grown in Britain.

But Sue Steptoe - who set up flower sales at Waitrose in 1994 - is keenest to talk about Kenya. The Waitrose Foundation is the charity through which the supermarket buys from Africa. I'm here, in Kenya, to visit rose farms that are part of the Waitrose Foundation scheme. The Foundation ploughs a percentage of profits back into social, economic and educational projects on farms in Africa. Every Waitrose Foundation-marked item that the customer buys will directly benefit the farm workers. (So far the Foundation has raised pounds 5.5m since its launch in 2005 and funded many projects). In addition, the roses are grown to LEAF standards (Linking Environment and Farming), which is essentially an environmental marque that tells the consumer that the producer operates in an environmentally responsible way.

Oserian, the first flower farm on Naivasha, was founded in 1982 and employs 4,800 people. A million stems per day trundle on to conveyor belts into the largest packing house in the world. It's epic. But step closer and the process is about deftness: each bunch is packed as attentively as befits a living gift. In 48 hours, these roses will be in a supermarket near you. To polite ridicule, I try to pack a bouquet myself. It is rejected by quality control.

Five years ago, the trade was in the spotlight. In 2007, British trade unionists funded a report by War on Want which found that flower farm workers in Colombia were exposed to long hours and illegal pesticides in order to supply cut-price romance to American consumers. In 2008, Maude Barlow, Canadian founder of Food & Water Watch, described Lake Naivasha as a "putrid puddle… the hippopotamuses are dying. They're baking in the sun."

This afternoon Lake Naivasha is brimfull, and hippos slobber and splash on their short legs. The water is at its highest since 1998, according to a surveyor's chart of the rise and fall of the lake over the last 50 years.

The white Kenyan founders of Oserian are proud of what they do. The farm has planted 300,000 saplings, built a hospital, a creche and four schools. Growing is done hydroponically, with bushes rooted in pumice stone crushed on the estate. Chemical usage has all but halved since 2005, thanks to phytoseilus, a spider mite which eats the most invasive bugs. Fungicide spraying is also reduced by pumping hot water into the greenhouses at dawn to prevent mould.

The water is heated by a borehole drilled 2,000m into the hot, volcanic rock of the Rift Valley. From the hilltop geothermal plant I begin to see the wider vision: founder Peter Zwager's estate is now 95 per cent wildlife sanctuary. He replaced 8,000 hectares of green beans with 230 hectares of roses. "Roses for Rhinos", as the World Wildlife Fund calls it, and soon we see eight white rhinos.

Self-reliance

"Fairtrade is the future for Kenyan flower farms who want to sell to Western Europe," Janice Kotut says. Her family business, Ravine Roses, is a drive into the steeper hills of Eldama, just across the equator and into a valley glittering with reservoirs of water siphoned off the greenhouse roofs. Like Oserian, the business has accreditation from the LEAF scheme as well as the Waitrose Foundation. Janice's father was born here in 1942 and the business began as her mother's hobby.

Janice did an MA at King's College, London, and worked in strategic brainstorming at Standard Chartered Bank before coming back to join the family business. Today Ravine Roses employs 1,000 people.

Unlike Naivasha - a new town, built for migrants drawn by the higher wages - Eldama was a village scattered through fields of maize and cattle. In the new library, "Entrepreneurship" is the most popular category. The path to the door is lit by solar power, funded by the Waitrose Foundation. It gets dark at six o'clock and the village committee voted first for street lights, so that shops can open after work and villagers do not have to stumble over pot-holes with paraffin lamps. A store for self-grown produce is the next project. It will be called "Jitegemee", a Swahili word which means "self-reliance". The highlight of my visit is the inauguration of a cattle dip. It's wonderful - and ever so slightly surreal - to be the audience for a choir chanting "Our Waitrose / You Make Us Happy".

Consumer responsibility

Back in London, I collect my thoughts in a cafe in Hackney. Beer is from the London Fields Brewery, bread from the E5 Bakehouse, and coffee is Fairtrade Colombian. And the peonies in the vase? "From the florist."

The eco-generation that takes the provenance of its food seriously still takes peonies in January for granted. Few will know that they were delivered to the florist in an HGV which has thundered through the dawn from the wholesale auction at Aalsmeer, Holland. This, one of the largest indoor spaces in the world, sells 20 million stems a day, flown in from as far afield as Australia or grown in the vast Dutch greenhouses which glow all night.

Independent scientific studies (including one produced for DEFRA by Dr Adrian Williams of Cranfield University) have calculated that roses grown in heated Dutch greenhouses have a much bigger carbon footprint than those airfreighted from Kenya.

Surprisingly, it is the supermarkets who have pioneered the ethical flower movement, not small, Dutch-dependent florists. "When my mother came to visit me in London," says Janice Kotut, "she was so proud to see the family's name on the label. And we can tell you which greenhouse that bunch came from."

But is it too easy to blame the Dutch? Any florist will tell you that few consumers ask: "Where are your flowers from?" Even fewer, they say, will pay more for British-grown flowers.

The industry is at a tipping point. In Kenya, Ravine Roses and Oserian continue to be in a minority. The majority of growers do not farm sustainably or build creches. And Lake Naivasha will continue to be an ecosystem under stress unless more farms reduce water and pesticide use.

But however wistful we might be for roses snipped from a dewy garden at dawn, the industry is here to stay. And ever since the British and Dutch battled for nutmegs in 17th-century Indonesia, the whims of Western consumers have transformed societies thousands of miles away. When, in the 1850s, Dr Livingstone trekked through Africa, he accepted that European trade would transform the Continent for ever. He argued with his fellow missionaries that that it was the Christian consumer's responsibility to choose what to buy, from whom, and for how much.

Buy the right cut flowers on Thursday and it is a win-win for consumer and community, whether it is the Isles of Scilly or the highlands of Kenya. Our choices do make a difference. The flower debate is where the food debate was 10 years ago. And think how much has changed, thanks to a pause for thought.

Christopher Woodward is director of The Garden Museeum in London