Flowering Mauna Loa silverswords in the managed breeding population at the Volcano Rare Plant Facility (credit: Silversword Foundation).

Mauna Kea Silversword (Argyroxiphium sandwicense subsp. sandwicense)

Mauna Loa Silversword (Argyroxiphium kauense)

These exotic silverswords, described as “radiantly beautiful,” get their name from their rosettes of long, silvery leaves. Both species are endemic to the volcanic regions on the Big Island of Hawaii. The Mauna Kea silversword originally encircled Mauna Kea volcano at heights between some 8,500 and 12,500 feet, and was the dominant species in both the alpine and subalpine ecosystems. Its sister, the Mauna Loa silversword, was once common in the wetter habitats on Mauna Loa and Hualalai volcanoes.

But in the late 1700s, the silverswords’ habitats were invaded by herds of sheep, pigs, and other herbivores introduced by the Europeans, and heavy grazing degraded the natural environment of the volcanoes. The silverswords gradually became less and less abundant and far less widely distributed, not surprising in view of the fact that by the 1930s the sheep population on Mauna Kea actually rose to more than forty thousand! At one point in the late 1990s, Mauna Kea silverswords remaining in the wild numbered fewer than forty individuals, all growing on cliff and rock faces that were quite inaccessible to ungulates.

The Mauna Loa silversword was less severely endangered at that time on Mauna Loa, where about a thousand plants survived in three separate locations—but they had gone altogether from Hualalai volcano. Both species are also threatened by the introduction of alien insects such as ants and wasps, which could potentially endanger the native bees that serve as pollinators for the silverswords.

Recently, I spoke on the phone with Dr. Robert Robichaux, who has been working with Hawaiian plants since the late 1970s, but since the early 1990s he and a group of close friends and colleagues have focused on the silverswords’ restoration. Rob’s interest in botany began when, at college, a friend suggested he take a plant anatomy course—simply because he needed an elective. “I didn’t know plants had anatomy, but I signed up and loved it.” When he heard, as a graduate student, that there was an opportunity to join a research project in Hawaii, where he had been surfing during his high school years, he jumped at it. And so his career path opened up as he fell in love with Hawaii and its spectacular native flora.

He told me of one really exciting day in 1996 during which he and several colleagues had been searching for remnant plants in a remote area of Mauna Loa, where silverswords had not been seen for two decades. Usually they are not hard to see, for the rosettes on mature plants are twelve to twenty inches in diameter. After hiking across lava for many hours, and near the point of giving up, they made an extraordinary discovery.

Kealii Bio and Rob Robichaux hand-pollinating a wild flowering Mauna Kea silversword on a cliff face (via ropes). Fewer than 30 plants remain in the wild population (credit: Hoala Fraiola).

“We were climbing over a small rise on one of the lava flows,” said Rob. “We paused to check our footing, looked down, and there, in a crack in the ground, was a perfect little rosette.” But it was only an inch and a half in diameter. “What the heck is this?” he had said, going down on his hands and knees. It was an old silversword plant! “After surviving years of browsing and trampling it was almost like a bonsai silversword.” After this initial discovery, Rob and several colleagues returned to the area. Searching now for very small rosettes, the group moved in widening concentric circles, often crawling on hands and knees, looking into crevices in the lava and into other spots where it was difficult for browsing animals to reach.

Hand-pollinating a Mauna Loa silversword in the managed breeding population at the Volcano Rare Plant Facility (credit: David J. Boyle).

“We stumbled on that one plant almost by chance,” said Rob. “It gave us a new search image, and in the end we found about 150 tiny survivors.” They took cuttings from many of the plants and flew them by helicopter to the Volcano Rare Plant Facility. “There, under the expert care of Patty Moriyasu, the cuttings rooted and grew rapidly, and more than a hundred flowered at the facility within the next three years.”

Protection of the Silverswords’ Environment
Large numbers of silversword seedlings have been successfully grown at the Volcano Rare Plant Facility destined for large-scale reintroduction. Protective fencing has been constructed around almost all of the sites where silverswords are being reintroduced in order to protect them from future browsing. Building fences across volcanic terrain has been an especially challenging task for the fence crews, as holes for the fence posts have to be drilled into hard lava.

The genetic diversity and health of the reintroduced plants are ensured through time-consuming hand pollination of flowering individuals, both in the greenhouse and in the field. Especially on Mauna Kea, the remnant silverswords grow in very inaccessible places—the steep cliffs and rock faces where browsing animals cannot go. No wonder Rob told me the fieldwork is often demanding and sometimes very precarious! He reminisced about dangling on the end of climbing ropes with fellow botanist Kealii Bio above a drop of forty to fifty feet in order to hand-pollinate some of the remnant surviving silverswords on Mauna Kea. “Kealii and I had to put absolute trust in the ropes,” he said, “as we each needed both hands free to work with the pollen and flowers.” (How much easier for a bee with wings!)

Getting Together to Save the Silversword
Several agencies and organizations collaborate in an informal public–private partnership to restore the silverswords. Different members of the partnership, such as the Hawaii Division of Forestry and Wildlife and the National Park Service, take responsibility and oversee planting in different areas.

By 2008, the total number of seedlings reintroduced in multiple sites on Mauna Loa and Mauna Kea exceeded forty thousand, Rob told me. Survivorship has varied from site to site, but in some places more than 95 percent of the seedlings have survived the critical first year. The ultimate goal is to restore the glorious silverswords of both species throughout their historic ranges.

Rob was realistic but hopeful about the future of the Hawaiian flora. “We used to wonder if it was hopeless, with so many species teetering on the brink of extinction,” he said. But they don’t think that anymore. “The challenges are daunting, to be sure, yet so many endangered plants are beginning to come back with help. There is a window of opportunity that remains open for us. If we can act swiftly enough, Hawaii’s critically imperiled flora may have a brighter future.”

Even more so if the children become involved. At some of the reintroduction sites, schoolchildren have actively participated in silversword planting efforts. “When you place an endangered silversword seedling in the hands of a young student and entrust her or him to plant it, nurture it, and monitor it, the effect can be transforming,” Rob told me. “Our hope is that many of the young students will become tomorrow’s leaders in conserving the unique plants and ecosystems of Hawaii.” The future of the silverswords will, one day, rest in their hands.