Britain's first olive grove is a sign of our hotter times

In one of the most remarkable signs yet of the advance of global warming, Britain's first olive grove has been planted in Devon.

Temperatures have risen so far in recent years that it is now considered possible to grow the iconic fruit of the Mediterranean countries commercially in southern England.

Several studies have suggested that, in decades to come, olives, vines and other warm-climate plants will be likely to flourish in a substantially warmer Britain. Now a Devon smallholder has taken the plunge and, in partnership with an Italian olive specialist, planted a grove of 120 olive trees on the banks of the river Otter near Honiton.

Mark Diacono, who is establishing a "climate change farm" on his land, intends his olives to be a commercial crop which will produce Britain's first home-grown olive oil, in five to seven years. He has planted them in co-operation with an Italian gardener living in England, Emilio Ciacci, who has provided the trees from the hills near his home at Maremma, Tuscany.

A 39-year-old environmental consultant, Mr Diacono has no doubt that UK temperatures are becoming suitable for olive cultivation. "There's no question that the climate is going to get there," he said. "It's just, have I done this 10 years too early or 20 years too early?

"But I don't think so. We don't need to turn into Portugal really, we just need it to be slightly warmer for longer, and we are making that shift. We are crossing that threshold."

Mr Diacono's rows of young trees with their distinctive grey-green leaves look incongruous in the red Devon earth, with the oakwoods of the Blackdown Hills in the background, in place of the glittering blue of the Mediterranean. Yet he is confident they will grow.

The saplings provided by Mr Ciacci and his English partner, Esther Yorke, come from a region of Italy that has frost and snow in the winter as well as baking temperatures in the summer. "They're pretty tough trees," Ms Yorke said.

Mr Diacono has also gone to considerable lengths to get the preparation right. He has deeply ploughed the soil to get at the river gravels underneath, which will help with drainage, and has undersown the trees with red clover, which will be used as a mulch to protect the roots from cold in winter.

His olives are a logical next step after the orchards of apricots and almonds he has already planted to take advantage of forthcoming climate change on his smallholding, which is undergoing conversion to organic status.

Mr Diacono said he saw global warming as a "vast" problem for society but he felt that people could take advantage of it and even help to combat it by growing produce that at present involves many "food miles" to be brought into Britain. "If there's a restaurant or delicatessen specialising in local food, the first cop-out is always olive oil, because they have to get it from abroad," he said. "If we could source it from England, that would be great."

There is no doubt the climate is warming steadily in Britain, as well as in the rest of the world. Since 1900, the average UK temperature has risen by about 1C, and the growing season has lengthened by about a month. Currently, the temperature is rising by between 0.15C and 0.2C per decade but the rate itself will increase and, by the 2020s, the climate will be nearly another full degree warmer than the average of 1961-1990.

According to the UK Climate Impacts Programme, very hot and dry summers of the sort Britain experienced in 1995 will strike in one in three years by the 2050s. Maximum temperatures in southern counties, such as Berkshire, which now reach about 34C (93F), will start to exceed 40C. By 2080, South-east England could become on average 5C warmer in summer, making it as hot as Bordeaux now.

"In a few years' time, the trees on Mark's land will look like a Mediterranean olive grove," said Ms Yorke, who with Mr Ciacci is starting a business based in Sherborne, Dorset, under the name Tuscan Trees, to try to promote olive groves across southern England.

"We want to be able to repeat what we have done with Mark with other people," she said. "We think there is now a real opportunity for olives to be grown commercially in Britain."