All change on the gardening front - and forget that lawn

Farewell, cool green lawn. So long, venerable yew hedge. It's been fun, bright herbaceous border, ablaze with delphiniums and lupins – but soon the time will come to say goodbye.

Many of the most archetypal features of the traditional English garden are likely to be lost to climate change in the coming century, a report said yesterday. They will disappear as summer temperatures rise, summer droughts become commonplace and winter rainfall increases.

In their place we will see a more Mediterranean and even tropical flora. There will be losses and gains, challenges and opportunities, the report, commissioned by the National Trust, the Royal Horticultural Society and the UK Climate Impacts Programme (UKCIP), said; but above all there will be change.

As the climate warms towards the middle of the century, by perhaps 3C a year on average, change will affect every horticultural enterprise, from the cottage garden to aristocratic parkland. There will be longer growing seasons, but more pests. There will be fewer frosts, but more chance of winter waterlogging. There will be more carbon dioxide in the atmosphere to help plants thrive, but less moisture in the soil in summer. And some plants will not survive.

The best-loved garden features, those most redolent of Englishness, will be the biggest losses, the report warned. The lawn will become ever more difficult to maintain in the form we have known it. There will be a nine or 10-month mowing season, from September right through to June, and then two months in high summer – just the time when we enjoy our lawns most – in which the grass stops growing or dies.

"Lawns will present real challenges," Andrew Colquhoun, the director general of the Royal Horticultural Society, said. "Some gardeners will give up the struggle and entirely move over to gravel or decking.For many British males a lawn is an obsession, and they may need psychological as well as horticultural advice."

The herbaceous borders so typical of cottage gardens will also become difficult to maintain because summers may be too dry for staples such as delphiniums, asters, lupins and phlox. Features of more formal gardens such as yew hedges might increasingly be vulnerable to fungus and pest attack. Some typical trees of parkland such as the beech, which has shallow roots, will have increasing difficulty enduring summer droughts, and the likelihood of more severe storms means more will be blown over.

What this means is that it will be hardest of all to maintain the great historical gardens such as Sissinghurst and Stowe, of which the National Trust is the prime curator.

Fiona Reynolds, the trust's director general, said: "Those of us who garden and conserve on the grand scale need to plan decades ahead. This issue was not even on the agenda a decade ago but is now one of our greatest challenges." At Sheffield Park, East Sussex, the trust is planting 9,000 new varieties of trees and shrubs in an effort to anticipate the warmer and more unstable weather.

Gardening will be harder work. Plants will grow taller, sturdier and longer, and will need more maintenance. Richard Bigrove, senior lecturer in landscape management at Reading University and joint author of the report, said: "There will be more of your neighbour's Leyland cypress hedge to get rid of each year."

But there will be pluses: earlier displays of spring bulbs, more spectacular autumn foliage and opportunities for what Mr Bigrove terms "adventurous gardening".

The Royal Horticultural Society has drawn up a long list of unfamiliar plants of which we can expect to see more. They include soft fruits such as grapes, pomegranates, citrus fruits, apricots and nectarines, palm trees and bananas, hedge plants such as acacia, oleander and myrtle, trees such as eucalyptus, fig and olive, and many smaller plants.

But the cool green English garden as we knew it is unlikely to remain.

ON THE WAY IN

The colours of the Mediterranean and of points even further south may become familiar to our children and grandchildren in their gardens, with the pale purple splash of bougainvillaea mixing with the white of orange blossom and its dark green leaves. Other citrus fruits will be grown. Expect to see more figs hanging from the branches, more grape vines; olives will be growing here as will bananas. "I'm not saying Essex will be covered in banana plantations," said Dr Andrew Colquhoun, the head of the Royal Horticultural Society. "But they will certainly be easier to grow." Various species of palm will flourish – date palms and fan palms – and trees we know from our trips abroad, such as Italian cypress and eucalyptus.

ON THE WAY OUT

The green lawn will be perhaps the greatest casualty of climate change. It will need a lot more maintenance and is likely to be brown and dry throughout the summer. The spiky blooms of the herbaceous border may go the same way. Delphiniums, lupins and other flower such as phlox and asters require deeply cultivated, fertile, moisture-retentive soil, which will be considerably harder to come by in the drier summers ahead. Plants needing cool temperatures – such as alpine flowers, the rhododendron shrub and willow trees – will be much harder to grow. Britain will present a harder environment for mosses and ferns too, and there will be difficulties for cool-loving plants of late winter and early spring such as snowdrops, crocuses, daffodils and bluebells.