Michael McCarthy: Return of the native: the great secret of 20th-century botany

The Silverdale Lady's Slipper is one of the very few examples of what is perhaps our most spectacular wild flower, a bloom very unlike the pale pastel spikes of the other British orchids. Cypripedium calceolous is an exotic, almost outlandish confection of banana yellow and maroon which might seem more at home in the tropics.

But the Silverdale plant itself is a bit of a mystery. It is not certain that it is entirely wild, and it may have been planted out. There are indications that it came from Central European stock. Dr Michael Fay, head of genetics at the Royal Botanic Gardens, Kew, has investigated the genome of the Silverdale plant and found that it is not closely related to native British orchids. "The Silverdale plant clearly doesn't fit in and the closest match we have got is Austrian," he said yesterday.

Not that that makes it any less worth seeing, of course. However, for most of the 20th century it was another Lady's Slipper which caused the greatest excitement, and was also the greatest secret, of British botany: a single plant, a true native, this one, found growing in a remote location in the 1930s, after the species had been declared extinct. (It had been greedily dug up by gardeners wherever it was found).

This single plant has been guarded round the clock in its flowering season for more than 50 years, and since 1970 it has had a special scientific committee fully devoted to its preservation. In 2004, after much asking, I was allowed to make a trip to see it at its secret site (nowhere near Silverdale), and the experience was unforgettable; if it looks spectacular in photographs, it's even more special in the wild.

In the 1990s, scientists at Kew discovered how to propagate it and planted out seedlings in other places; several have now flowered, and the Lady's Slipper appears to have been saved.