By David Bryant, Director of Communications
Today, a rooted cutting of the Kalalau hau kuahiwi is growing on Kauaʻi. If you held this fragile plant in your hands, you would be holding a generational story of struggle and determination, an embodiment of hope for a Hawaiian species once feared lost.
The famed cliffs of Kauaʻi’s Kalalau Valley are cloaked in emerald layers of plant life. Amid this lush tapestry, clinging to the sheer, wind-carved drops above the valley floor, grows the only known population of Kalalau hau kuahiwi (Hibiscadelphus woodii). This is an extraordinarily rare Hawaiian plant—its name, meaning “mountain hibiscus”, reflects its lofty habitat and delicate beauty.
Echoing the elegant curve of native honeycreeper beaks, the plant’s yellow blossoms hint at the vital role these birds once played in its pollination. It was these distinctive yellow blossoms, along with other clues, that signaled to field botanist Ken Wood—suspended on rappelling gear during a 1991 expedition—that he might be looking at a species unknown to science. Since that pivotal discovery, conservationists have worked tirelessly to bring this plant, teetering on the edge of extinction, into cultivation. Collaborative partnerships between the National Tropical Botanical Garden (NTBG), Hawaiʻi’s Division of Forestry and Wildlife (DOFAW), and other committed collaborators have helped hope take root for this imperiled species.
Since its initial discovery, the Kalalau hau kuahiwi has faced many challenges. Over the years, natural disasters like landslides and the relentless impact of invasive species took their toll. A boulder crash wiped out several of the few known individuals, leaving only one lingering specimen. Noble attempts at propagation through grafts, air layering, and cross-pollination repeatedly failed, and by the early 2000s, the species was feared extinct.
In 2016, a new chapter began with NTBG’s drone program coordinator Ben Nyberg. Using drone technology, Ben and Ken rediscovered the Kalalau hau kuahiwi in previously unreachable areas of the valley using drones. This breakthrough, featured in National Geographic, was a game-changer. “Finding it was an incredibly encouraging experience,” Nyberg said. “It made us hopeful both for the species and the potential of drone technology in plant conservation broadly.”
Ben and Ken identified a small cluster of surviving plants hidden away on the cliffside. Traditional methods couldn’t access the plants, so the team turned again to new technology. Ben began a collaboration with Outreach Robotics to develop a drone-based tool that could retrieve cuttings from steep, vertical areas. Enter the “Mamba.” Outreach Robotic’s invention allowed our teams to remotely and expediently collect plant cuttings from cliff habitats — a big step forward for conservation technology.
In April 2024, after many practice runs and successes collecting other species, Outreach Robotics and our team returned to Kalalau Valley to retrieve cuttings of the Kalalau hau kuahiwi. On that fateful day, 33 years since Ken had first found the plant on those rugged cliffs, the Mamba delivered cuttings safely into his hands.
While this was an incredible milestone, there was no time to waste. Hawai’i state botanist Matt Keir, who had helped orchestrate this initiative, quickly took the cuttings back to Oʻahu where his DOFAW colleagues were ready to propagate a plant that—until that point— had never been successfully propagated before.
Propagating the Kalalau hau kuahiwi has long been a daunting challenge—an endeavor marked by decades of valiant attempts and fragile hope. As Matt explains, “all species of Hibiscadelphus are extremely rare,” with some vanishing before meaningful cultivation efforts could even take root. “There’s been a history of cultivation with (Hibiscadelphus) species that were rediscovered on Hawaiʻi Island, and there’s a long history of people caring for these species and trying to recover them with the best of their ability.” To prepare for cultivating cuttings of the Kalalau hau kuahiwi, Matt and partners scoured the records, including old email exchanges, and interviewed horticulturalists who had achieved success with other Hibiscadelphus species.
The breakthrough came with a deceptively simple yet revolutionary tool: the fog box. Originally developed by horticulturist Doug Okamoto who retired from UH Mānoa’s Lyon Arboretum, this innovation creates an environment of constant, high humidity produced by an ultra-fine mist. The fog box can provide enough moisture to keep semi-hardwood and hardwood cuttings physiologically active without encouraging rot. DLNR horticulturalists Tiffany Lum, Ami Beasley, and Corbin Bennua—who all once worked under Doug—were tasked with rooting the Mamba-collected cuttings of the Kalalau hau kuahiwi. Using the fog box method, the team was able to get one cutting to take root—marking the first time the species had ever been propagated successfully.
Yet, even this milestone demanded patience and precision. “It took eight months just to see a single root emerge,” Matt notes. The fragility of the process means that optimism remains cautious. “You don’t get optimistic until roots actually come out the bottom of the pot.” This achievement, though fragile, represents a critical step in preserving a species that, until now, represented both a figurative and very real cliffhanger.
Bringing the rooted cutting back to Kauaʻi is an emotional moment. “There are a lot of highs and lows in conservation,” Ken reflects. “It becomes hard for those of us intimate with the Hawaiian flora to watch ecosystems change so dramatically, but ecstatic moments like this bring a certain joy—they keep us going.”
The future of the Kalalau hau kuahiwi hinges on long-term conservation efforts. There are plans for more drone-facilitated cuttings and ongoing propagation efforts. The ultimate goal is to establish a living collection that could produce viable seeds and, eventually, reintroduce the plant to its native habitat.
However, challenges remain. Factors like inbreeding, habitat loss, and the disappearance of its bird pollinators complicate efforts to ensure the plant’s long-term survival.
The rooted Kalalau hau kuahiwi is not the result of a single innovation but a testament to the strength of collaboration. From NTBG’s pioneering drone program to DOFAW’s specialized propagation facilities and the decades-long dedication of many conservationists, every partner brought unique expertise to the table.
“These extinctions don’t have to happen. It’s technically possible to prevent them—it’s a matter of will,” says Matt. As the saying goes, where there’s a will, there’s a way. “You can do ridiculous things, like sling-load robotic arms up a cliff, grab pieces of a plant, and bring them into a fog chamber.” These novel approaches, powered by partnerships, have led to a renewed future for the Kalalau hau kuhiwi and underline the far-reaching possibilities for endangered plant conservation broadly.
