The most important new species of palm for 50 years has been discovered by a family picnicking in the jungle.

Tahina spectabilis soars 60ft (18m) as it puts out millions of flowers in a spectacular last hurrah that kills it. Despite its size it escaped detection until Xavier Metz, a plantation owner, took his family for a picnic in Madagascar.

Dr Bill Baker, of the Royal Botanic Gardens, Kew, said finding the plant was equivalent to a zoologist identifying a new species of elephant hidden in a jungle. “It’s the most astonishing new palm in the last 50 years,” he said. “It’s absolutely enormous.”

The palm lives for several years until growing a “candelabra” structure upon which millions of flowers appear. These drip with nectar, making the palm a magnet for birds and insects. The energy the palm has to put into reproduction depletes its reserves and it dies of self-inflicted exhaustion.

The palm is located in a small area of the west side of Madagascar rather than the wetter east where most of the island’s palms are found. It is thought that only a hundred exist.

The new species, whose name is announced in the Botanical Journal of the Linnean Society today, has leaves which, with a 16ft diameter, are among the largest seen in flowering plants.

John Dransfield, joint author of The Palms of Madagascarand an honorary research fellow of Kew, said that when he saw Mr Metz’s photographs of the tree, “I could hardly believe my eyes. I couldn’t wait to examine specimens in detail.” Kew’s experts discovered that it was not just a new species but represented a genus never seen on Madagascar before. “It is very difficult to explain how it could ever have reached Madagascar,” Dr Dransfield added.

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