[7][8] The silversword alliance is considered the most dramatic example of adaptive radiation among plants in Hawaii, illustrating the role of isolation and distinctive ecological conditions in promoting evolution.

[9] The Mauna Kea silversword is an erect, single-stemmed and monocarpic or rarely branched and polycarpic basally woody herb, producing a globe-shaped cluster of thick, spirally arranged, sword-shaped silvery-green floccose-sericeous, linear-ligulate to linear-lanceolate leaves growing in a rosette.

[7] The Mauna Kea silversword evolved to survive extraordinarily harsh subalpine conditions where virtually no other plants could grow.

Sherwin Carlquist, who first established the ancestral role of California tarweeds in the evolutionary history of Hawaiian silverswords, speculated that their mainland precursor species may have had a resin unappetizing to herbivores.

[13][14] Protective advantage, however, favored the tarweeds and silverswords in their unique ability to store water as intracellular gel, an adaptation that would have made it possible for the species to live in arid environments.

Earliest accounts of the range of the Mauna Kea silversword do not suggest rarity; dead stalks were gathered for firewood by explorers in 1825.

[6] The first documentation of its decline dates to 1892, when it was said to have been once abundant but is "now nearly extinct except in the most rugged and inaccessible places.”[6] The thriving population was reduced to a few individuals in 25 years by a series of land use decisions.

[6] The sheep population on Mauna Kea eventually exceeded 40,000 in the 1930s, decimating the defenseless native plants including remaining silversword.

[4] Feral sheep were then greatly reduced from 1936 to 1950 but protected until 1981 as sport game in the Forest Reserve lands, which overlap the original Mauna Kea silversword habitat.

[6] Initial efforts to save the Mauna Kea silversword focused on fencing off the few known remaining plants, primarily from early cultivation attempts.

[6] The Mauna Kea silversword was declared a federal endangered species in 1986,[15] and only 41 naturally occurring plants survived in the wild in 2003.

[6] The University of Hawaiʻi Botany Department has published a 1987 photo which they claim shows the only known natural population of the Mauna Kea silversword at that time, a few individuals on cliffs above the Wailuku River which were unreachable by any foraging mammals.

To counter the effects of inbreeding, scientists began a controlled crossing program, hand-pollinating flowering silverswords in both the wild and nurseries.

Despite its logistical challenges, hand pollination was judged the most likely method to achieve fertilization and increase genetic exchange between nursery and wild individuals.

Nonnative honey bees (Apis mellifera) visit the flowers, but appear to steal pollen rather than move it between plants.

[3] In 1999, more than 2500 additional silverswords were planted on Mauna Kea at multiple protected sites, and plans were in place to reintroduce more every year.

[2] The United States Fish and Wildlife Service reports that there are now 8,000 individuals of the species outplanted on Mauna Kea, though they were still derived from only six wild founders.