Chelsea Flower Show growers hit by climate change as warm spring accelerates growth

Britain's warmest April has caused unprecedented challenges for the nurserymen and women exhibiting at the horticultural highlight of the year, the Chelsea Flower Show.

Last month's record temperatures mean that spring is up to a month in advance of its normal period over much of the country - and as a result, the flowers being carefully nurtured for Chelsea, which opens a week on Monday, have been blooming far too early.

A panoply of gardening tricks is having to be employed by growers to hold back the march of nature and keep prize specimens from "going over" before the Royal Horticultural Society's flagship annual event, one of the world's premier gardening festivals. Those tricks range from cold stores and dark tunnels, to constant movement of plants in and out of light and warmth, repeated deadheading - and even individual "straitjackets" for flower buds.

The latter technique is being used on peonies at Kelways nursery in Langport, Somerset, which is providing flowers for the firm's own stand in the show's centrepiece, the Grand Pavilion, as well as for several individual gardens. "Because of the incredible weather we had, everything is a month in advance of normal, so for me and a lot of other people, this is the most challenging Chelsea ever," said Kelways' general manager, David Root.

The company's Chelsea-destined peonies have now been put into a cold store to retard their growth, and as an added restriction, individual jackets made of a strip of foam material have been tied around each flower bud to prevent it blooming.

It sounds a simple enough operation - until you realise that there are more than 1,000 of them. When they are transported to London next weekend, they will go, for the first time, in a refrigerated lorry.

"The plants we grow for Chelsea flower naturally in early May, so for us to get them to flower three weeks later is a challenge at the best of times, even in normal circumstances," Mr Root said.

"But this year they have grown so rapidly they had to go into the cold store. The temperature is 38F and there is total darkness. They will stay there until we take them to the show."

Kelways is also growing irises for Chelsea, which have provided a different set of problems. "They cannot be cold-stored, so we are growing them in the shade of an open-sided barn," said Mr Root. "But they naturally turn towards the light, so to prevent them kinking, we have to turn each one every other day." How many blooms does that particular manoeuvre involve? "There are 1,200 of them."

Similar mass effort is necessary on the other side of England at the British Wild Flower Plants nursery at North Burlingham, Norfolk, which is growing native British flowers such as wild clary, cow parsley and ragged robin for Chelsea, as well as a series of Californian flowers.

"As a rule of thumb, everything is three weeks to a month ahead of normal so yes, preparing for this year's Chelsea has been tricky," said the nursery manager, Paul Chapman. "We've been moving things around all the time, from the field, to the glasshouse, then back into the field, and sometimes into the shade tunnel, to hold them back.

"I estimate we have spent an extra two weeks' work this spring just moving stuff around."

Deadheading has also been a major task for Mr Chapman. "If you let a plant flower and don't take the dead head off, the plant will set seed, and feel it's done its job, and stop flowering," he explained.

Another problem has been a plague of pests. Jekka McVicar, who is growing organic herbs at Alveston, near Bristol for her Chelsea exhibit, has found so many greenfly on plants such as lettuce and mint that she has had to brush them off with a dry paint brush (not being able to use pesticides as an organic grower). "It's very time-consuming," she said.

Some of the 47 individual show gardens at Chelsea, which will be planted during next week, are having to substitute plants they intended to show with later-flowering species.

Chris Beardshaw, who is recreating an Edwardian country house garden, said that columbines, for example, which had already flowered, were having to be replaced with achilleas. "Normally you would not expect achilleas to flower until late June or even early July," he said.

The effects of a warming climate can clearly be seen at Chelsea, said the RHS shows organiser, Bob Sweet. "We are now seeing plants that would have been completely out of season 50 years ago.

"Then, we would have seen a lot of rhododendrons and camelias but they are mostly over now. Instead we are seeing plants like pelargoniums, which once you would have struggled to get in flower by this time."

The RHS Chelsea Flower Show takes place on 22-26 May 2007 (22 & 23 May: RHS members only - 22 & 23 May all day tickets now sold out). Tickets must be booked in advance on 0870 247 1226 or by visiting the website www.rhs.org.uk/flowershows