The team at the National Pinetum at Bedgebury, Kent, said they had broken new ground with the Vietnamese golden cypress Xanthocyparis vietnamensis.
Bedgebury curator Chris Reynolds and his assistant Dan Luscombe visited Hanoi four years ago to help locals conserve endangered conifer species. They scaled remote mountains to pinpoint the few remaining known golden cypresses.
Last May they sowed seeds in the Kent nursery and six seedlings geminated five months later. The number has since increased to 18 and in four years the team hopes to plant them in the Pinetum.
They will join nine other golden cypresses grown from cuttings donated by Royal Botanic Gardens Edinburgh and planted in 2005. Despite the colder British climate, all are doing well.
The project was part of the Global Trees Campaign to secure the future of threatened species and tap into their benefits for humans and the wider environment. Other initiatives involve saving baobabs in Madagascar and magnolias in China.