The world's most mysterious and elusive orchid lives underground in Australia. Scientists are trying to rescue this botanic marvel from going completely extinct.

As a child, Kingsley Dixon's favourite book was Orchids of the West, about the wild orchids of Western Australia, where he lived. There was one illustration in particular that left him transfixed: an ink drawing of Rhizanthella gardneri, commonly known as the Western Australian underground orchid.

"From when I was tiny, I used to just look at this page and go: 'oh my, there's an orchid, it lives underground, it doesn't have leaves, it doesn't have roots, and it has this fabulous flower!'" Dixon recalls.

A self-described "little plant geek", he spent much of his time in the Australian bush – the wild scrubland near his home in Perth – collecting orchids and then growing them on at home. "By the age of 13, I had a large collection of bush orchids, but the one sitting in the middle of the book, the Western Australian underground orchid – that was the dream, the dream of my life," he says. The closest he got as a child was seeing a preserved specimen in a jar, during a special trip to a herbarium for his birthday. It would take him years to finally spot one in the wild, during a field trip to the small town of Babakin in Western Australia in 1982, when he was 24. "We stopped for a cup of tea [...] and I wandered into the bushland and kicked some soil only to reveal some coloured bracts [of the orchid]," he recalls. "It was an absolute Eureka moment."

Today, Rhizanthella gardneri is the one of the world's rarest orchids and critically endangered due to habitat loss, with only a tiny number of plants surviving in the wild. The number fluctuates from year to year and in recent years has been as low as three or even none found at all, Dixon says, with climate change adding further pressure on the species. "It went in my own lifetime from [seeing] it, to watching this species slip away," he says. So Dixon, now a professor of botany at the University of Western Australia and the former director of Kings Park and Botanic Garden in Western Australia, has a new dream: to save the underground orchid from extinction.

Rhizanthella gardneri is not only the world's rarest orchid, it is also one of the most mysterious. It's the only known plant that flowers underground. It also grows, germinates and sets seed totally underground, and is thought to be pollinated by termites.

The orchid is able to survive underground thanks to an intricate and complex three-way alliance: it connects to an above-ground plant, the Melaleuca uncinata bush, through a white, thread-like fungus. The connecting fungus transfers nutrients from the bush to the orchid.

This kind of beneficial bond with fungi, known as a mycorrhizal association, is in fact typical of orchids in general, says Jacopo Calevo, a plant ecologist and orchidologist who has researched orchids and climate change in Europe and Western Australia. To understand how climate change affects orchids, one has to therefore look at the whole picture, he explains – the orchid, its special fungus, and in the case of the underground orchid, the Melaleuca uncinata bush as well.

"It's estimated that about

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