A once-thriving native plant is sprouting again on Maunakea after more than a century of near-extinction.
Silverswords, or Argyroxiphium sandwicense, are a strange-looking flowering shrub whose narrow leaves shine silver and reflective in the sun.
The plants were once so common on the Big Island that Maunakea was said to seem snowcapped, said Patti Heidenfeldt, native plant restoration assistant for the University of Hawaii’s Center for Maunakea Stewardship. But by the 1890s, non-native animals such as cattle, sheep and goats had ravaged the shrubs.
By 1984, a census determined that the silverswords on Maunakea had been reduced to only 131 plants, only 15 of which had naturally propagated. Heidenfeldt said all the rest of the plants had been cultivated by humans.
The plants also face other existential threats. Silverswords thrive in low-humidity climates between 8,500 feet and 12,500 feet, but Heidenfeldt said climate change threatens to shrink the plant’s viable habitat on the mountain.
But the critically endangered genus may yet make a comeback. A project by the Center for Maunakea Stewardship hopes to raise a new population of silverswords to take root on the mountain.
That’s easier said than done, however.
“In order for these plants to propagate, you need two of these plants to be flowering at the same time, and for them to not be from the same family,” Heidenfeldt said.
Silverswords can flower at any age between 5 and 90 years old, but because they die after flowering, and due to the general dearth of silverswords on the mountain, natural propagation is all but impossible.
Instead, Heidenfeldt said CMS has taken pollen samples from silverswords that flowered years or even decades ago and used them to fertilize a new crop of seedlings. About 130 silversword sprouts — “my babies,” Heidenfeldt called them — have successfully taken root in a greenhouse about halfway up Maunakea.
“It’s the first time we’ve been able to do this,” Heidenfeldt said, adding that while there are still some silverswords growing in a nearby fenced-off area, those plants were raised in nurseries, not on the mountain.
Another batch of sprouts are being raised at a nursery at Hawaiian Volcanoes National Park, Heidenfeldt said, which tests whether the species can survive different climate conditions.
Eventually, Heidenfeldt said, the sprouts in the greenhouse will be planted in strategic areas throughout Maunakea, in places fenced off to protect them from ungulates. She guessed that the first round of plantings will take place around February, and a new batch of seedlings will begin growing at the greenhouse.
After they’ve been planted, Heidenfeldt said the silverswords will be monitored to ensure they remain safe and healthy, and also to obtain pollen samples when they start flowering.
Heidenfeldt said a self-sustaining population of silverswords on the mountain could be feasible, but only if the ungulate population was significantly reduced or eradicated. Because silverswords are succulents, they are an attractive source of water for herbivores in the arid parts of the mountain.
But for now, Heidenfeldt said this effort to reintroduce the plants to their native habitat has gone better than expected. With a lot more work, she said, the mountain may bloom silver again some day.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.
