High on a sea cliff on the Hawaiian island of Kauai grows a strange and very special plant. Its grey stem is swollen at its base to conserve water, and atop the stem sits a rosette of shiny green leaves. “It sort of looks like a cabbage on a bowling pin,” says Steve Perlman, the botanist who has repeatedly risked his life to save it from extinction.

The plant is Brighamia insignis, and it’s a species with many problems. Like 90 percent of Hawaii’s 1,200 native plant species, it grows nowhere else on Earth. And like hundreds of those species, it is under threat. The International Union for the Conservation of Nature’s Red List ranks it as critically endangered. Perlman wants to stop it joining the more than 100 Hawaiian plant species that have already gone extinct.

Hawaii is a special place. For millions of years its species evolved in isolation, free from our distorting influence. That all changed around 1500 years ago when the first Polynesian people arrived.

Those original Hawaiians found in Brighamia insignis a minor pharmacy. They ate the plant raw to treat tuberculosis, or mixed its crushed leaves with salt to treat infected cuts. They may even have cultivated this plant for its medicinal properties, as they did with its close relative Brighamia rockii on the island of Molokai. But overall, the arrival of people in Hawaii spelled trouble for Brighamia insignis.

The Polynesians and, more so, the Europeans who arrived in the 1700s, disturbed the local ecology, bringing new species that could out compete the native ones. Feral goats, rats and invasive weeds have all taken their toll. Many species suffer from such a surfeit of enemies, but Brighamia insignis has also lost a friend: the insect it relied upon to pollinate its fragrant flowers.

Each flower is made of five petals that are fused along most of their length so they form a long trumpet shape that opens to form a five-pointed star. The nectar is so far from the opening that only the long proboscis of a butterfly or moth could reach it.

Perlman thinks its natural pollinator is a large moth called the fabulous green sphinx of Kauai. This species is so rare that until 1998 it was thought to be extinct, not having been seen for decades. No pollination, meant no seeds, no future generations to replace the older plants that died each year. “That is why I began doing the pollinating,” says Perlman.

In the 1970s, he spearheaded action to save the species. The plant’s rarity called for extreme measures. To find Brighamia insignis, Perlman first had to take to the sea, battling rough waves in a bright red canoe to reach otherwise inaccessible parts of the rugged coastline. He then had to haul himself up the sheer sea cliffs without a rope.

Video footage of Perlman in action makes for dizzying viewing. As he climbs, his fingers dislodge great chunks of crumbling rock. “It is exciting and thrilling to say the least”, he says. “But that is where the plants are.”

Only once he was on the clifftop, 3,000 feet above the sea, could he secure a rope. Now the botanising could begin. Perlman abseiled back down the cliff, bouncing himself across its face in search of Brighamia insignis plants. He patiently transferred pollen between plants, by hand, to ensure they would produce seeds. He would return months later to harvest the seeds, so they could be grown into adult plants in controlled conditions.

Back in the 1970s when Perlman began working with Brighamia insignis there were a couple of hundred of these plants on Kauai. But two hurricanes wiped many of them out. “As far as we know there is only one plant left in the wild on Kauai,” he says. The species no longer exists on Ni’ihau, the other island where it once grew.

But thanks to Perlman’s bravery and dedication, there are now hundreds of thousands of Brighamia insignis in cultivation, especially in Europe, where they are now popular houseplants. Perlman and colleagues at Hawaii’s Plant Extinction Prevention Program have also planted hundreds of their nursery-grown plants back in the wild.

“We will not lose this species,” says Perlman. In rescuing Brighamia insignis, he learnt cliff-climbing skills that have benefited many other rare plants. But of all the species Perlman has worked with in his 44 years of botanising, Brighamia insignis and its sister species Brighamia rockii are his favourites.

“I love to work with them on the cliffs where they grow,” he says. “I like their shape with the large swollen base and long fragrant flowers. They grow in incredible places in Hawaii and it is a thrill to have helped save them from extinction.”

For Perlman it is personal. He has witnessed the extinction of twenty species, something he has described as being like losing a family member. The main reason he endeavours to save Brighamia insignis, is simply because it exists, and so deserves to endure. This curious plant may have lost its pollinator, but in Perlman at least, it has found a new best friend.

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A version of this article first appeared in BBC Earth magazine.

Photo credit: Forest Starr and Kim Starr  (Wikimedia / Creative Commons)