Climate change could threaten traditional garden features from lupins to lawns, Britain's National Trust warned yesterday as it launched an exhibition celebrating centuries of horticultural heritage.
The Trust, which looks after 200 gardens and collections of plants built up over hundreds of years, hopes the touring exhibition will provide a "wake-up call" over the possible impacts of temperature rises on traditional British horticulture.
According to the Met Office Hadley Centre and the UK Climate Projections, a 2°C rise in temperatures could make southern England's climate similar to southwest France, while a 4°C rise could expose gardens to conditions more like southwest Portugal.
Herbaceous borders and water-loving English country garden plants from foxgloves to delphiniums could struggle in hotter drier summers, while milder, wetter winters could threaten spring bulbs such as tulips and hyacinths.
But plants from hotter climates such as passion flowers and cacti would thrive in warmer temperatures.
Trees such as beeches and chestnuts could be hit by drier conditions, more disease and stormy weather, and traditional orchards could be replaced by nectarines, oranges or even bananas as the UK warmed.
Lawns would vanish - and be replaced by gravel - if we headed towards temperature rises of 4°C, while water features would become a thing of the past.
The changes to how British gardens might look in the future are being highlighted in a series of paintings by Gloucestershire artist Rob Collins, which form part of the A Plant in Time exhibition.
The initiative, backed by the Yorkshire and Clydesdale Banks, is touring Trust properties around the country and encouraging people to make paper flowers to create a massive artificial flower show.
Celebrity gardener Alan Titchmarsh, who is backing the initiative and has made his own paper flower, said: "The historic plant collections in National Trust gardens are the horticultural equivalent of the collections in our national galleries and museums.
"Many people are unaware just how important these living treasures are, but make a flower for A Plant in Time and you'll stop and appreciate them a bit more."
The scheme also allows people who are inspired to take action to help the environment make a "green living pledge" on a paper leaf.
Mike Calnan, the National Trust's head of gardens and parks, said he hoped the initiative would translate the science of climate change into people's back gardens.
Mr Calnan said there was a great awareness of the potential impacts on polar bears, ice sheets and ice caps.
"This exhibition is a gentle reminder that this amazing heritage here in the Trust is equally under threat."
While he said much of what could happen to UK gardens in the future was uncertain, he warned: "Climate change is possibly going to shunt gardens into a different climatic zone."
He said the Trust was undertaking an inventory of plants at 80 important gardens to see what was most under threat or coming to the end of their lives, and propagating new, more vigorous stock which it is hoped will survive better.
The gardens are also bringing in eco-measures such as rainwater harvesting, "green" heating systems for greenhouses and composting facilities. And a long-term policy is being drawn up which is considering moving at-risk plants to more suitable locations in the same garden, such as shadier or damper corners, or to other local sites or even further afield to protect prize specimens if it is felt it is worth doing.