If you thought that all the world's rarest trees were only in virgin rainforest or on remote tropical islands, then prepare to be surprised. Brett Westwood joins botanist Tim Rich from the National Museum of Wales to look for the whitebeam trees, which are found nowhere else in the world. Ley's whitebeam near Merthyr Tydfil has only 17 specimens growing in the wild, and new species are still being described from the Avon Gorge in Bristol. Thanks to analysis of their DNA we know more than ever about these trees and their conservation presents some fascinating challenges.
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