The population of the Ka'u silversword is down to 600 on its home ground on Mauna Kea, according to the Fish and Wildlife Service's recovery plan. The plants grow in wet country between 5,000 and 8000-feet elevation. This plant's spike leaves are longer than those of the more familiar Haleakala silversword, and they're not as hairy, thus not quite so silvery. The Ka'u silversword can grow to 4 feet in height before the massive flower stalk adds another 3 to 6 feet. They live many years, but die after flowering once.
Pigs root up plants in bog habitats.
The Haleakala silverswords are protected by the National Park Service, which has an extensive fencing and a goat control program to protect them. Kahuku Ranch, Sierra Club volunteers, the state Department of Land and Natural Resources have worked to improve the protection, but the recovery plan said controlling the feral animals is critically important. The silverswords don't readily fertilize themselves so there needs to be at least two different plants flowering the same time for good seed production. That's why small populations are at risk. Early in this decade, only a few hundred remained.