The appearance of the National Collection of Dahlias at the Chelsea Flower Show in the month of May is pretty unusual, if not outstanding.

That was the 40-year dream realised by the advisor to the collection, Jon Wheatley, who rightly earned a coveted Gold Medal and the President's Award, given to the best exhibit in the Grand Pavilion.

The dahlia normally gives us that splash of colour late summer and into early autumn, so how did he defy the natural cycle and get more than 70 cultivars to flower three months ahead of schedule?

"It was a real challenge," said Jon. "My whole life for the past year has revolved around the show deadline of May 14. Some of it was pure luck - only two dahlias required artificial light and one, dahlia tenuicaulis, the largest of the species dahlias, came into flower just for the show, which was a real fluke."

"We grew them with growers Michael Twining near St Michael's Mount, Cornwall, from cuttings in November and December. From pots to flower, it took 60-70 days and not all the varieties flower at the same time so I lost what little hair I had left getting them to all bloom at once." That wasn't the only logistical problem - Jon was commuting from Bristol to monitor their progress.

The national collection has been held for the past 10 years by Winchester Growers and is based in Penzance, which normally has a milder climate than the rest of the UK. But that counted for nothing this year as Cornwall had its worast winter for 10 years.

Michael Mann, Operations Director for Winchester Growers, said: "It got to the point six weeks out when we nearly made the call to pull the plug on exhibiting. Then we had that 10-day fine spell and that just got us over the finishing line."

"I got pretty emotional when I heard the result," admitted Jon. "It's the first time pot dahlias have been at Chelsea and more than 40 years that the national growers have been here, so my lifetime ambition is fulfilled."

Jon, who has extensive horticultural knowledge and is a member of the Executive Council of the National Dahlia Society, is already looking ahead to the Hampton Court Palace Flower Show (http://www.rhs.org.uk/whatson/shows/hamptoncourt2009/), which takes place from July 7–12. "You're only as good as your last result," he said.

The National Collection (www.national-dahlia-collection.co.uk) has public open days in August. Winchester Growers are one of the country's leading suppliers of dahlias (www.winchestergrowers.co.uk).

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