The quintessential English garden is under threat from climate change and gardeners must adapt or see their plots wither and die from the effects of hotter summers and dry winters.
New types of drought-resistant Mediterranean plants, restricted water use and imaginative garden design would all have to become part of the gardens of the future, Ian Pearson, the environment and climate change minister, warned yesterday.
Speaking at the Royal Botanic Gardens at Kew in south-west London, Mr Pearson said: "The quintessential English garden is under threat [and] will have to adapt to our changing climate. Gardeners have a responsibility in water use, species type and garden design to adapt too."
In a speech almost drowned out by the noise of aircraft approaching Heathrow, the minister said the struggles faced by gardeners during the July heatwave and the continuing drought, together with the effect of past carbon emissions, would become commonplace in the future. "This will put gardeners in the frontline of climate change," he said.
Plants would flower, seed and die more rapidly than before and become more prone to pests and diseases that thrive without cold winters to kill them off. There would also be more damage from storms, causing flooding, he said.
Experts at Kew say gardeners should focus less on traditional English cottage garden flowers, such as roses, primroses and rhododendrons, and plant more drought-resistant plants like lavender and rosemary, which are more suited to a Mediterranean climate. Among trees, shallow rooting birches and rowans, crab-apples, some maples and magnolias would suffer while chestnut-leaf oaks and cedars would thrive. Fruit trees might also suffer from lower yields, said Tony Kirkham, the head of Kew's arboretum. "Trees need a rest each year - dormant periods each year to recover from growing, which they are getting less of at the moment," he said.
Mr Kirkham said measures were being taken at Kew which had lessons for gardeners. Irrigation was being cut and kept at surface level to save water; green waste was recycled for compost and leaves were left and mowed up on lawns as food for worms, which in turn helped aerate and break up the soil. Lawns were also cut back from around some heritage trees so that the ground above their roots more resembled woodland. "If we want to preserve the traditional English garden, we are going to have to spend a lot more time there," he said.
One of the worst-hit trees at Kew is the horse chestnut, which has been hit by the leaf mining moth, introduced from Macedonia in 2002 and thriving in warmer winters. As The Independent revealed last month, the moths produce caterpillars which eat into the leaves, which wither and fall, making the trees appear much more "autumnal". Mr Kirkham said: "Although the trees will bloom again in the spring, they are severely weakened and we do not know if they will survive in the long term."
A study by Kew shows that four out of five species of flowering plants were flowering nine to 15 days earlier than they were 20 years ago. They included the oak, which is flowering 10 days early, rowan (15), box (15) and cow parsley (nine). The horse chestnut showed no change.
Sir Peter Crane, director of Kew, said there was "real cause for concern" over climate change and the gardens were acutely aware of the problem. Significantly, as one of the places that epitomises the glories of the English landscape, next year's Summer Festival will be dedicated to the Mediterranean.
Shrivelling in the heat
Primula vulgaris, or the common primrose, thrives in damp soil
The finely cut leaves of Japanese maples (Acer) scorch in dry conditions
Flowering times for traditional English roses are being accelerated by heat
Horse chestnuts are under threat by a moth that thrives in warmer winters
Dryopteris filix-mas, the male fern, prefers cool, shady conditions
Rhododendrons are being targeted by new fungal diseases
Ornamental cherries, like fruit trees, require a cold, dormant period in winter
A mature beech (Fagus sylvatica) can require 220 litres of water per hour
Magnolias will shed their leaves early in order to combat drought
Fruit trees, such as crab apples (Malus), may suffer from a lower yield
Most varieties of birch (Betula) tend to prefer a moist, well-drained soil
Rowans (Sorbus) are among trees that will suffer in warmer conditions