In recent times it has become the axiom of environmentalism. The closer to Britain something is produced, the less carbon dioxide is expelled in its importation.

But the wisdom of “food miles” has been challenged in a report indicating that carbon emissions for importing Kenyan roses, including air freight, were almost six times lower than for roses imported from the Netherlands.

The report, carried out by the natural resources department at Cranfield University, suggests that the high environmental cost of artificially heating and lighting roses in the Netherlands significantly outweighs emissions caused by flying them from Kenya.

Hilary Benn, the Secretary of State for International Development, will make a speech on Tuesday on a similar theme, telling shoppers not to boycott African-grown flowers for Valentine’s Day.

The study, commissioned by World Flowers and Sainsbury’s, indicated that carbon emissions for Kenyan roses, including air freight, were just 17 per cent of those for Dutch roses.

The report studied a Kenyan farm that supplies Sainsbury’s with its roses, and analysed energy consumption and CO2 emissions for growing, packing, cooling and transporting the roses to the UK, factoring in fertilisers, pesticides, vehicles and materials used.

These were compared with data from a grower in the Netherlands, where artificial light and heat replaced sunshine as a source of light and heating.

Adrian Williams, who carried out the research, said: “The main difficulty is that in Holland you need to provide artificial light and heat in order to keep the flowers growing. It’s plausible that you would find a similar outcome with foods that we would grow close to home in a greenhouse situation or import from overseas.”

The study found that 6,000 kg of CO2 was released per batch of Kenyan roses, as opposed to 35,000 kg for production in the Netherlands.

Whereas 99 per cent of the Dutch emissions were caused by producing the roses, only 7.3 per cent of the CO2 produced by the Kenyan flowers was caused by growing them there. In contrast, 91 per cent of CO2 emissions from the Kenyan roses were accounted for by the 4,000 air miles clocked up in importing them to the UK. Less than 1 per cent of the Dutch grower’s emissions were caused by transport.

Yields of roses in Kenya are approximately double those of the Netherlands, owing in no small part to the year-round sunshine. The development of boxes that can be packed efficiently into aircraft was also cited as a factor in reducing emissions.

Alison Austin, Sainsbury’s head of brand policy and sustainability, said: “What this shows is that it is not as simple as avoiding products from far-flung places. It’s about gathering information to make an informed carbon choice.”

Flower companies are drawing up eco-friendly guidelines in an attempt to assuage mounting consumer concern surrounding sourcing and “flower miles”.

Interflora, the UK’s biggest flower delivery network, said that it was putting together a series of “green” guidelines for its members in response to a surge in consumer interest in its sourcing policies. A spokeswoman said: “We are consulting with bodies such as the Carbon Neutral Company.”

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