The future of gardening under global warming – when summer temperatures are expected frequently to exceed 40C (105F) across Britain – was unveiled at Kew yesterday.

Long hot summers combined with wetter and milder winters are expected to drive many popular plants out of flower beds, but leave room for a wide range of Mediterranean blooms.

Fragile favourites dependent on regular watering will disappear but horticulturists at the Royal Botanic Gardens, Kew, insist that keen gardeners will still be able to grow stunning flowers.

Two Mediterranean gardens and a beach area complete with sand and coastal plants were opened at Kew to help to show how to adapt to climate change. One of the new garden areas featured an olive grove while the second replicated plants seen in a typical Iberian cork oak forest.

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They have been planted with species that are well adapted to the arid summers and wet winters that are seen in Mediterranean areas and that are expected to be increasingly common in Britain. Summer temperatures have yet to hit 40C in Britain, though they came close in 2003 with 38.5C, but by 2080 such scorchers are forecast to be commonplace.

Winters are expected to be affected just as much. Snow and frost are predicted to be all but distant memories except on high ground, and there should be much more rain.

Nigel Taylor, a horticultural curator at Kew, said that the Mediterranean gardens had been created because even in the past 20 years there had been “extraordinary changes” in weather conditions.

Since the mid1980s Kew, in common with much of the rest of Britain, has experienced an absence of sustained cold winter weather and since 1990 has been through ten of the hottest years on record.

Dr Taylor gave warning that the carefully tended lawns beloved by Britons will either vanish or need to be allowed to grow long and unkempt.

Searingly hot summers will, he said, dry out organic material which will be eaten by bacteria, leaving the soil dry, dusty and littered with exposed rocks and stone. To cope with the changing conditions he said that gardeners would have to grow different plants. Temperatures even now are suitable for many of them, including the olive, which he says will thrive and fruit.

Among the flowers that will replace clematis, pansies and roses will be salvias, brooms, wormwoods and rock roses, but they are likely to have to be more spaced out in the beds because of competition for the limited moisture available.

Herbs such as rosemaries, thymes and lavenders will thrive even more than they do now but instead of sitting in the shadows of native trees such as beeches and oaks they will live alongside olives, cork trees and fantail palms.

Gardeners will have to change their habits, not just their plants, and as temperatures rise they will, said Dr Taylor, find they have to work at different times of the year.

While all but the keenest amateur gardeners are most active during the warmer months, they may find themselves having to go outside in the middle of winter instead to carry out weeding and pruning.

Lawns are already having to be mown throughout the winter and Kew has stopped sending its mowers for service in January, as was traditional. Instead, mowers are overhauled during August. In previous years the grass needed regular trimming during the middle of summer but more recently has virtually stopped growing in August.

John Lonsdale, Kew’s horticultural manager, said that many Mediterranean plants did most of their growing in the winter when it was cooler and wetter. With careful selection of plants it would be possible to provide thick ground cover in most parts of the garden and to ensure that there were as many flowers as there are today.

“It can be just as colourful,” he said. “And it will be more aromatic than gardens are today.”

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